Calf nutrition from birth to breeding

Effects of kefir fermented with or without 1% autolyzed yeast powder on dry matter intake, intestinal permeability, and rumen fermentation profile of Holstein calves

Co-fermenting kefir with Saccharomyces cerevisiae has been shown to enhance the exopolysaccharides (EPS) produced by lactic acid bacteria during fermentation, which may further promote intestinal development in the calf. Four different concentrations (0%, 0.25%, 0.5%, 1%) on a weight/weight basis (g/20 g kefir grain) of either dried, activated distiller's yeast or autolyzed yeast powder were evaluated for EPS optimization in kefir, and inclusion of 1% autolyzed yeast powder resulted in the greatest EPS yield. In a randomized, complete block design, 81 Holstein heifers were enrolled at 3 d of age, blocked by birth weight, and randomized within block to receive either 125 mL salable whole milk (CON), 125 mL of kefir (KEF), or 125 mL of kefir fermented with 1% autolyzed yeast powder (YAK) in milk replacer 1x/d until 28 d of age. Feed intake and health scores were recorded daily for each calf through 1-week postweaning (63 d of age). Growth measurements were recorded weekly until 9 wk. Indigestible markers D-mannitol and Cr-EDTA were administered at 15, 29, and 50 d to a subset of calves (n = 36) and recovered in plasma and serum to measure intestinal permeability. Rumen fluid was collected from calves (n = 35) via gastric tube at 63 ± 2 d to measure pH and VFA concentrations, as well as serum BHB at 14, 28, 42, 56, and 63 d. While health outcomes (diarrhea, respiratory illness, dehydration) were not affected by treatment, supplementation with YAK significantly improved starter DMI and BW in the preweaning period compared with CON and KEF, and postweaning DMI was significantly improved in both KEF and YAK compared with CON. Increased butyrate was observed in rumen fluid of calves fed YAK, though serum BHB was not affected. This work contributes to further understanding kefir as a promoter of gastrointestinal development in calves and the potential benefits of EPS in the developing ruminant.

Preweaning nutrient supply improves lactation productivity and reduced the risk of culling in Holstein cows

This study aimed to investigate the impact of preweaning nutrient intake on milk production of the 2 first lactations, risk of culling and metabolomic profiles in dairy cows fed a restricted (RES) or an elevated (ELE) milk supply preweaning. A total of 86 Holstein Friesian female calves were randomly assigned to either 5.4 Mcal of ME in 8 L of MR/d (ELE) or 2.7 Mcal of ME in 4 L of MR/d (RES) from d 2 after birth until they were stepped down by 50% from d 42 to d 49 and fully weaned at d 50. Starting from d 50, animals from both treatments were fed and managed in the same way, with treatments being blinded, for the entire study duration. At 60 d in milk (DIM) in first lactation, blood samples were taken for metabolomics analysis. Heifers fed the ELE diet exhibited higher ADG (0.79 vs. 0.49 kg/d) in the pre-weaning period, leading to higher BW at 70 d of age (94 vs. 85 kg). In the first lactation, cows fed the ELE diet preweaning exhibited higher DMI (+ 0.7 kg/d), higher milk fat yield (+ 50 g/d) and milk fat content (+0.24%) but lower feed efficiency (-0.04) compared with the RES group. In the second lactation, fat- protein corrected milk yield (+ 1.8 kg/d), milk fat yield (+115 g/d), milk fat content (+0.22%) and feed efficiency (+0.06) were all higher in ELE cows. Throughout these 2 lactations, ELE cows were leaner as indicated by a lower BCS. Cows fed the ELE diet preweaning had a higher first service conception rate during the second lactation compared with RES (40.7 vs. 13.0%). Moreover, the likelihood to be culled before third, fourth, or fifth calving was halved when calves were fed ELE as compared with RES. Metabolomic profiling revealed distinct metabolomic profiles at 60 DIM in response to preweaning milk supply. The major metabolic pathways affected by preweaning nutrient supply at 60 DIM were pyrimidine, sphingosine, guanidino and acetamido, purine metabolism, and the tricarboxylic acid cycle. The metabolic profile differences between the groups describe a metabolic configuration that was sustained into adulthood and that may explain the improved productivity and resilience of cows fed a greater milk supply during the preweaning period.

Effects of preweaning milk allowance on long-term metabolism in Holstein heifers

Suboptimal preweaning nutrition of dairy calves has been causally associated with impaired adult metabolic health and lactation performance. However, the biological mechanisms linking early life nutrient supply and future performance remain insufficiently understood. Thus, the objective of this study was to characterize growth, reproductive performance, glucose metabolism, and the metabolic profile of growing heifers fed a restricted (RES) or an elevated (ELE) milk supply preweaning. Heifer calves (n = 86) born from a single herd of ∼120 dairy cows were blocked in pairs by the dam's parity and birth date. Within block, calves were fed an identical colostrum supply and randomly assigned to a milk replacer (MR) allowance level treatment of either 5.41 Mcal of ME in 8 L of MR/d (ELE) or 2.71 Mcal of ME in 4L of MR/d (RES). The MR (150 g/L), containing 24% crude protein, 18% crude fat, and 45% lactose, was fed from d 2 after birth until calves were stepped down by 50% at d 49 and fully weaned at d 56. All calves were kept in individual hutches until wk 10 and had ad libitum access to fresh pelleted calf starter, chopped wheat straw, and water. Starting from wk 8, heifers from both treatments were fed and managed in the same way, and preweaning treatments were blind to caretakers. Blood samples for metabolomics analysis were collected at 330 d of age, and an insulin-modified intravenous glucose tolerance test was conducted at 370 ± 12 d of age. Heifers fed the ELE diet exhibited higher average daily gain in the preweaning period, leading to higher body weight at 70 d of age (+ 9 kg). At 330 d of age, growth advantages were no longer significant, and preweaning nutrition had no effect on age at first service, first service conception rates, age at conception, or number of services per conception. The metabolomic serum data sampled at 330 d of age revealed that carnitine, glycerolipid, and purine metabolism were predicted to be significantly affected by preweaning nutrient supply, reflecting long-term metabolic programming. At 370 d of age, during the first 20 min following the glucose infusion, blood insulin levels were greater (10.3 ng/mL vs. 7.7 ng/mL), the area under the curve for insulin tended to be greater, and insulin sensitivity was lower in RES heifers. Increasing the amount of MR fed to calves preweaning had a sustained impact on metabolic processes, but long-term differences could not be detected in growth or reproductive performance, potentially due to the low number of animals.

Changes in Ruminal Fermentation and Growth Performance in Calves After Increasing Ruminal Undegradable Protein at Two Different Time Points Pre-Weaning

The cost-effective rearing of heifers depends on the provision of adequate nutrients at an appropriate age to meet nutrient requirements for growth and production. The objective of the present study was to investigate how the time of switching to a rumen-undegradable protein (RUP) source affects the ruminal fermentation and growth performance of Holstein dairy calves. A total of 36 Holstein female calves were randomly allocated to one of three dietary treatments on day 28 or 42 of life. In the first 28 days of life, they were on the same soybean meal (SBM)-based starter diet containing 22.2% crude protein with 37% RUP. The RUP content of the experimental diet was increased to 48% by a total replacement of the original SBM with xylose-treated soybean meal (XSBM). The following treatments were used: (1) starter diet containing SBM from d 28 (SBM28); (2) starter diet containing XSBM from d 28 (XSBM28); and (3) starter diet containing XSBM from d 42 (XSBM42). All the calves were fed a constant amount of milk (4 L/d), weaned on day 60, and then remained in the experiment until day 70 of life. The results showed that neither feed intake nor BW were influenced by the treatments in the pre-weaning period (days 28 to 60). The calves fed the XSBM28 and XSBM42 diets had greater daily gain and gain-to-feed ratio compared to those on the SBM28 diet post-weaning from day 61 to 70 (p < 0.05). The inclusion of XSBM in the starter diets from days 28 and 42 increased the calves' height pre- and post-weaning (p < 0.05). The ruminal pH and concentrations of butyrate and iso-butyrate were higher at weaning when the calves were fed the XSBM diets. The calves fed the XSBM diets had less ammonia-N and total short-chain fatty acids at day 70 of life (p < 0.05) and a lower neutral detergent fiber digestibility in the post-weaning period (p < 0.05). The fecal scores and blood metabolites were not different among the treatments. The results showed that increasing the RUP content from 37% to 48% in the starter diets by a total replacement of SBM with XSBM during the pre-weaning period may improve the growth performance around weaning. A later replacement at 42 days of life appears equally effective compared to a replacement at 28 days of life.

Performance, nutrient digestibilities, and metabolic profiles of Holstein calves fed whole milk or milk replacer at 2 feeding levels

The macronutrient composition of common milk replacers (MR) largely differs from bovine whole milk (WM). These differences are more nutritionally relevant when calves receive higher milk allowances. Therefore, the present study compared fresh WM with a conventional MR fed at 2 level of feeding allowances evaluating growth performance, apparent total-tract nutrient digestibilities, N balance, and serum metabolite profiles in calves. Newborn male Holstein calves (n = 48; 1.96 ± 0.99 d of age; 45.0 ± 4.37 kg BW) were blocked by arrival date and age. Calves in each block were then randomly assigned to the 4 treatments (n = 12 per treatment): MR or WM at a high (9.0 L/d) or low feeding allowance (4.5 L/d) fed 3 times daily. Calves were weaned between wk 6 and 10 following the introduction of the starter feed in wk 6. The study ended 13 wk after the arrival at the facility. Blood and body weights were collected on arrival, and weekly thereafter. Total 24h-collection periods of feces and urine was performed at wk 2, 4, 5, 7, 9, 11, and 13. Remarkably, no interactions were observed between liquid feed and level of supply. Calves fed MR had higher ADG during the preweaning phase than to calves fed WM. However, calves fed WM had an increased growth rate postweaning, resulting in no difference in BW at the end of the study. Calves fed WM had a higher apparent crude fat digestibility during the weaning period. Metabolic N efficiency, expressed as N balance relative to digestible N supply, was higher during the preweaning phase, but tended to be lower during the postweaning phase for calves fed MR as compared with calves fed WM. In the preweaning period, serum glucose, BHB, nonesterified fatty acids (NEFA), total protein (TP), urea, albumin, globulin, triglyceride (TG), and cholesterol were influenced by liquid feed source. Carryover effects of milk source on TG and TP were observed during the postweaning period. As expected, calves fed a high milk allowance showed better ADG at preweaning and were consistently heavier throughout the study than calves fed a low milk allowance. Feeding a high milk allowance did not negatively affect nutrient digestibility during the postweaning phase. In the preweaning phase, milk allowance affected glucose and cholesterol metabolism, whereas TG, TP, albumin, and NEFA concentrations were affected during the postweaning period. From a single oral dose of indigestible markers (Cr-EDTA, lactulose, and d-mannitol), calves fed a high milk allowance showed greater urinary recovery of all markers after 6 h of collection, but not after 24 h. Calves fed a high milk allowance had a higher proportion of days with lower fecal scores during the preweaning phase. In conclusion, the serum metabolite profiles of calves throughout the study were highly influenced by milk source. Higher milk allowance increased growth performance and had no adverse effects on starter feed intake or nutrient digestibility in the postweaning phase. The multiple effects described for milk source and level of supply were overall independent, presenting no relevant interactions.

Evaluation of changes in calf management from 2012 to 2022 on Austrian dairy farms using an online questionnaire

Calf management is important for the development, health, and welfare of the animals. In this follow-up study, we evaluated calf management practices on dairy farms in Austria using an online questionnaire in 2021 and 2022. We tested the hypothesis that farmers changed calf management on their farm within these 10 years. The total number of analyzable surveys in 2022 was 2,314. All variables changed significantly between years. Therefore, farms were chosen randomly by controlling for confounding changes in herd size (number of dairy cows), farm type (conventional vs. organic), and type of cows' barn (freestall vs. tiestall). From 2012 to 2022, the median number of cows per farm increased from 20 (interquartile range [IQR] 13 to 30) to 22 (IQR 13 to 35), and the percentage of organic-producing farms increased from 23.9% (2012) to 30.6% (2022). The number of farms offering colostrum within 4 h after birth increased from 83.7% to 87.2%. This change was significant when subsampling was performed. The quantity of first colostrum offered to the newborns was mainly 2 to 4 L (69%), with an increased percentage of farms offering less than 2 L (13.3% vs. 18.3%). The percentage of farms testing colostrum quality using an objective method (hydrometer, Brix refractometer, outflow funnel) increased significantly by 4.9-fold and was 9.4% in 2022. On most farms (88.8% and 86.6% in 2012 and 2022, respectively), calves were housed individually after birth. A higher percentage reported grouping calves at an earlier age than in 2012. In both years, mainly whole milk was fed (85.1% vs. 86.3%). The number of farms where nonsalable or waste milk was fed to calves decreased significantly from 84.0% to 74.1%. Milk allowance increased nonsignificantly. Subsampling revealed that the age at weaning increased significantly between years. The most important health problem in calves was diarrhea (in 59.8% of farms, >10% of calves; and in 27.4%, >25%), followed by respiratory tract disease (in 39.8% of farms, >10% of calves; and on 16.4%, >25%). Compared with 2012, in 2022, a significantly higher percentage of farmers stated that they had a calf diarrhea incidence of >10% (39.8% vs. 59.8%). In our study, weak points regarding calf management on farms were not offering enough first colostrum, missing testing for colostrum quality, not housing calves socially in the first weeks postnatum, and feeding restricted amounts of milk. The median mortality rate of 3% (IQR 1 to 5) and increasing diarrhea incidence also show that calf management practices need improvement. Thus, how to get farmers motivated to implement changes in their management in accordance with science-based recommendations remains an open question.

The Impact of the Lactation Period Gut Microbiota of Two Different Beef Cattle Breeds on Spring-Born Calves

To investigate the impact of maternal microbiota during lactation in different beef cattle breeds on their own immune levels, milk quality, and the growth and development of their offspring, this study measured the immune parameters, intestinal microbiota diversity, and milk quality of Pingliang red cattle and Simmental cattle, and performed a correlation analysis with the growth and development of their offspring. Our study showed that during lactation, Pingliang red cattle had significantly higher IL-6 levels than Simmental cattle, while the latter exhibited higher levels of immune factors such as IgG, IgA, IgM, IL-1β, and TNFα. The analysis of the intestinal microbiota of lactating cows found that Pingliang red cattle were rich in Bacteroidetes and Fibrobacteres, while Simmental cattle had a higher proportion of Actinobacteria. This difference may be related to the different adaptation strategies in energy metabolism and immune regulation between the two breeds. In addition, the analysis of milk quality between different beef cattle breeds revealed significant differences in protein, acidity, milk fat, and total solids. The correlation analysis found that Alistipes_communis, Firmicutes_bacterium_CAG_110, Alistipes_communis, Paludibacter_propionicigenes, Alistipes_sp._58_9_plus, and Bacteroidales_bacterium_55_9 were associated with both milk quality and the growth of offspring calves, including body weight, body length, chest girth, and cannon circumference. In conclusion, this study provides new insights into the intestinal microbiota, immune characteristics, and their effects on offspring health in different beef cattle breeds, and has important implications for breed selection and management strategies in the livestock industry.

Farm and Animal Factors Associated with Morbidity, Mortality, and Growth of Pre-Weaned Heifer Dairy Calves in Southern Brazil

This study investigates morbidity, mortality, and weight gain in pre-weaned female dairy calves, which pose economic and animal welfare challenges for farms, particularly in family-run operations in southern Brazil. We aimed to identify the rates and factors associated with these outcomes in Alto Uruguai, Rio Grande do Sul, Brazil, tracking 547 calves from 70 farms across 27 municipalities from July 2015 to September 2016. We assessed calf-rearing practices, nutrition, health, and the environment using farmer questionnaires, direct observations, and systematic weight and health monitoring of female calves from birth to weaning. The association between predictors and perinatal mortality (stillbirths and deaths within 24 h), postnatal mortality (deaths from 25 h after birth to weaning), calf morbidity, and weight gain was analysed through regression models. The participating farms had 25 (9-70) (median and range) lactating cows and produced 411 (96-1631) L/d of milk (median and range). Total mortality rate was 6.8% (median 0, range 0-50%/range), of which 2.4% (median 0, range 0-50%/range) was perinatal and 4.5% (median 0, range 0-40%/range) postnatal. Average morbidity was one case for every five calves born alive (106/538), 83% of which were reported as diarrhoea cases. Weight gain was 570 ± 212 g/d (mean and standard deviation). The postnatal mortality rate was highest in the first few weeks of life and among calves with at least one case of diarrhoea. Younger and winter/spring-born calves became sick more frequently. The calves of purebred bulls, fed with cow's milk, which received at least 4 L of milk and 0.5 kg of feed daily, had greater weight gain. The calf mortality rate was at the lower end of the range reported in international research. The main disease affecting calves was diarrhoea, and weight gain was insufficient for calves to double their weight by the time they were weaned. The results of the present study suggest that the quality of the management adopted in calf rearing in many of the family-run dairy farms of southern Brazil may be compromising the welfare, health, performance, and survival of the calves and possibly the productivity of dairy herds.

The microbiota: a key regulator of health, productivity, and reproductive success in mammals

The microbiota, intensely intertwined with mammalian physiology, significantly impacts health, productivity, and reproductive functions. The normal microbiota interacts with the host through the following key mechanisms: acting as a protective barrier against pathogens, maintain mucosal barrier integrity, assisting in nutrient metabolism, and modulating of the immune response. Therefore, supporting growth and development of host, and providing protection against pathogens and toxic substances. The microbiota significantly influences brain development and behavior, as demonstrated by comprehensive findings from controlled laboratory experiments and human clinical studies. The prospects suggested that gut microbiome influence neurodevelopmental processes, modulate stress responses, and affect cognitive function through the gut-brain axis. Microbiota in the gastrointestinal tract of farm animals break down and ferment the ingested feed into nutrients, utilize to produce meat and milk. Among the beneficial by-products of gut microbiota, short-chain fatty acids (SCFAs) are particularly noteworthy for their substantial role in disease prevention and the promotion of various productive aspects in mammals. The microbiota plays a pivotal role in the reproductive hormonal systems of mammals, boosting reproductive performance in both sexes and fostering the maternal-infant connection, thereby becoming a crucial factor in sustaining mammalian existence. The microbiota is a critical factor influencing reproductive success and production traits in mammals. A well-balanced microbiome improves nutrient absorption and metabolic efficiency, leading to better growth rates, increased milk production, and enhanced overall health. Additionally, it regulates key reproductive hormones like estrogen and progesterone, which are essential for successful conception and pregnancy. Understanding the role of gut microbiota offers valuable insights for optimizing breeding and improving production outcomes, contributing to advancements in agriculture and veterinary medicine. This study emphasizes the critical ecological roles of mammalian microbiota, highlighting their essential contributions to health, productivity, and reproductive success. By integrating human and veterinary perspectives, it demonstrates how microbial communities enhance immune function, metabolic processes, and hormonal regulation across species, offering insights that benefit both clinical and agricultural advancements.

Serum lipidomic profiling of dairy calves fed milk replacers containing animal or vegetable fats

Vegetable fat blends are commonly used as fat sources in milk replacers (MR) for calves, but their composition differs considerably from that of bovine milk fat. The aim of this study was to investigate the serum lipid profile of preweaning calves fed twice-daily MR containing 30% fat (% DM). Upon arrival, 30 male Holstein-Friesian calves (BW = 45.6 ± 4.0 kg, age = 2.29 ± 0.8 d) were randomly assigned to 2 experimental diets (n = 15 per treatment): one MR was derived from either vegetable fats (VG; 65% rapeseed and 35% coconut fats) or animal fats (AN; 65% packers lard and 35% dairy cream). The 2 MR formulas contained 30% fat, 24% CP, and 36% lactose. Calves were housed indoors in individual pens with ad libitum access to chopped straw and water. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 13.5% solids. An untargeted liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) method was employed to analyze the lipid profiles in the serum of calves sampled from the jugular vein at 35 d of age. In total, 594 lipids were characterized, comprising 25 different lipid classes. Principal component analysis (PCA) showed significant separation between VG and AN, indicating different lipid profiles in the serum. An orthogonal partial least squares discriminant analysis (OPLS-DA) classification model was used to further validate the distinction between the 2 treatment groups. The model exhibited a robust class separation and high predictive accuracy. Using a volcano plot (fold change threshold ≥1.5 and false discovery rate ≤0.05), it was observed that calves fed AN had higher levels of 39 lipid species in serum than calves fed VG, whereas 171 lipid species were lower in the AN group. Lipid classes, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM), triglycerides (TG), lysophosphatidylcholine (LPC), and lysophosphatidylethanolamine (LPE), were different. In particular, PC and PE were observed at lower levels in calves fed AN, possibly indicating shifts in cell membrane characteristics, intracellular signaling, and liver functions. In addition, a decrease in certain triglyceride (TG) species was observed in calves fed AN, including a decrease in TG species such as TG 36:0 and TG 38:0, possibly related to variations in the content of certain fatty acids within the AN MR, such as C10:0, C12:0, C14:0, and C18:0, compared with the VG MR. Calves fed AN had lower levels of LPC and LPE, and lysophosphatidylinositol, SM, and phosphatidylinositol species than calves fed VG, suggesting shifts in lipoprotein and lipid metabolic pathways. In conclusion, these results deepen the understanding of how lipid sources in MR can modulate the serum lipidome profiles of dairy calves.

Incremental supply of fat, lactose, or protein influences the diurnal pattern of heat production and substrate oxidation in preweaning calves

Increasing nutrient supply to dairy calves has well known benefits; however, the effects of milk replacer (MR) composition when supplied in higher amounts are not fully understood, particularly in the first weeks of life. To better understand the metabolism of macronutrient supply in young calves (21 d old), we investigated diurnal patterns of heat production and substrate oxidation in young calves fed MR with an incremental supply of fat, lactose, or protein. Thirty-two groups of 3 mixed-sex Holstein-Friesian newborn calves (3.4 ± 1.6 d of age), were randomly assigned to one of 4 dietary treatments and studied for 21 d. Diets consisted of a basal MR (23.3% CP, 21.2% EE, and 48.8% lactose of DM) fed at 550 kJ/kg BW0.85 per day (CON; n = 24), or the basal MR incrementally supplied with 126 kJ of digestible energy/BW0.85 per day as milk fat (+FAT; n = 23), lactose (+LAC; n = 24), or milk protein (+PRO; n = 23). Calves were fed MR in 2 daily meals and had ad libitum access to water, but were not supplied with any calf starter nor forage. After 2 weeks of adaptation to the diets, groups of 3 calves were placed for 1 wk in an open-circuit respiration chamber for nitrogen and energy balance measurements (lasting 7 d). On d 3, glucose oxidation kinetics was estimated by using [U-13C]glucose. Measurements included total heat production (total energy [HP], activity [Hact] expenditure, resting metabolic rate [RMR]), respiration quotient (RQ), carbohydrate (COX) and fat oxidation (FOX) in 10 min. intervals and averaging these values per hour over days. Incremental supply of lactose and fat increased body fat deposition, with observed patterns in RMR indicating that this increase occurred primarily after the meals. Specifically, the average daily RMR was highest in the +PRO group and lowest in the CON treatment. The HP was higher in the +PRO group and throughout the day, hourly means of HP were higher in this treatment mainly caused by an increase in Hact. The recovery of 13CO2 from oral pulse-dosed [U-13C]glucose was high (77%), and not significantly different between treatments, indicating that ingested lactose was oxidized to a similar extent across treatments. Increasing lactose supply in young calves increased fat retention by reduction in fatty oxidation. Calves fed a MR with additional protein or fat raised RMR persistently throughout the day, whereas the extra lactose supply only affects RMR after the meal. Dietary glucose was almost completely oxidized (77% based on (13C) glucose measurement) regardless of nutrient supplementation. Extra protein supply increased HP and FOX compared with similar intakes of fat and lactose. Fasting heat production (FHP) of young, group-housed calves is comparable to literature values and unaffected by energy intake. Overall, these findings deepen our understanding of how different nutrients affect metabolic processes, fat retention, and energy expenditure in young dairy calves.

Effects of bulk tank milk, waste milk, and pasteurized waste milk on the nutrient utilization, gastrointestinal tract development, and antimicrobial resistance to Escherichia coli in preweaning dairy calves

This study aimed to assess the effect of bulk tank milk (BTM), waste milk (WM), and pasteurized waste milk (PWM) on nutrient digestibility, ruminal and cecal fermentation, gastrointestinal tract (GIT) development, and antimicrobial resistance of fecal Escherichia coli from dairy calves at 2 periods (30 and 60 d of age). Calves were grouped according to BW, serum protein levels, and breed composition. Three treatments were included: BTM (n = 21), WM from cows under antibiotic treatment (n = 21), and PWM (WM submitted to HTST pasteurization; n = 21). A total of 63 calves were used, of which 18 animals (n = 6 per treatment) were evaluated in the period of 4 to 30 d, and 45 (n = 15 per treatment) from 4 to 60 d. During the experimental period, a daily intake of 6 L of milk was divided into 2 equal meals, with ad libitum access to water and starter. Milk and feed intakes were recorded daily. Apparent total-tract digestibility and nitrogen balance were conducted from 25 to 29 d of age (n = 6) and from 53 to 57 d of age (n = 15). Animals were slaughtered at 30 ± 1 and 60 ± 1 d of age for the assessment of ruminal and cecal fermentation and GIT development. Antimicrobial susceptibility testing was conducted at 1, 30, and 60 d of age (n = 15/treatment). Statistical analysis used a linear mixed-effects model for continuous outcomes and generalized linear models for single measurements (R software). Treatments WM and PWM had lower rumen pH, higher ruminal acetate concentration, larger reticulorumen and liver, and a higher prevalence of fecal-resistant E. coli compared with BTM at both 30 and 60 d. Up to 60 d, both BTM and WM treatments exhibited higher digestibility of ether extract and gross energy compared with the PWM, whereas WM and PWM treatments showed increased nitrogen intake and retention compared with the BTM treatment. These findings suggest that pasteurization of WM negatively affects nutrient digestibility and calf performance, while also affecting rumen development. Additionally, the use of milk containing antibiotic residue leads to the selection of resistant E. coli in the GIT over time.

Effects of milk replacer powder added to pasteurized whole milk over different durations on dairy calves fed ground starter diet with alfalfa hay

Adding milk replacer powder (MRP) to whole milk during the entire preweaning period can increase growth but raises concern because of low starter feed intake and slumps in ADG at weaning and postweaning. In the current study, effects of adding MRP to pasteurized whole milk (PWM) during d 10 to 41 or d 10 to 59 of age were investigated in comparison with PWM. Calves (24 females and 21 males; 39.8 ± 1.85 kg BW) were randomly allocated to 1 of 3 treatments: (1) conventional protocol, 5 L/d PWM from d 3 to 56, and 2.5 L/d from d 57 to 59 of age (CONV; TS intake = 31.9 kg), (2) short duration of adding MRP to PWM protocol, 5 L/d PWM from d 3 to 9, 5 L/d PWM + MRP (18% TS) from d 10 to 41, 5 L/d PWM from d 42 to 56, and 2.5 L/d PWM from d 57 to 59 (SHD; TS intake = 42.3 kg), (3) long duration of adding MRP to PWM protocol, 5 L/d PWM from d 3-9, 5 L/d PWM + MRP from d 10-56, 2.5 L/d PWM + MRP from d 57-59 (LD; TS intake = 47.7 kg). The osmolality of PWM and PWM + MRP was 278 and 519 mOsm/L, respectively. Calves were weaned on d 60, and the study terminated on d 75. There was a treatment × time interaction for starter intake, where intake was greater for CONV than other treatments from d 14-41 and was greater in CONV than LD during d 42 to 48 and d 56 to 62 of age. Final BW was lower in CONV calves than LD calves. Weaning BW and overall hip height were lower in CONV calves than other treatments. The CONV calves had lower ADG at d 14 to 27 and d 35 to 41, and SHD calves had lower ADG at d 42 to 48 than other treatments. Calves fed CONV treatment had lower ruminal acetate and greater propionate than SHD calves during preweaning. Calves fed LD treatment had lower total VFA and tended to have greater ruminal pH than other treatments. Calves fed CONV had greater neutrophils and neutrophils/lymphocytes ratio and lower lymphocytes than other treatments. Glucose concentration was greater for LD versus other treatments at d 56, and lower for SHD versus other treatments at d 70 of study. Insulin concentration and homeostatic model assessment of insulin resistance index were greater in LD compared with other treatments during preweaning but were not different postweaning. Serum BHB was greater in CONV than other treatments. Albumin was greater for CONV versus other treatments at d 56, however, it was greater in LD-fed calves at d 70 of study. Results indicate that feeding a PWM + MRP to the calves during the entire preweaning period resulted in lower starter feed intake around weaning, but overall starter intake was similar with a greater final BW and fewer health-related issues throughout the study. Shifting a PWM + MRP to the conventional whole milk at d 40 of age decreased the ADG of calves.

Fat composition of milk replacer influences growth performance, feeding behavior, and plasma fatty acid profile in ad libitum-fed calves

Fat composition in milk replacers (MR) for calves differs from bovine milk fat in multiple ways. The aim of the study was to investigate the impact of different approaches of formulating fat in MR on growth, ad libitum intakes of MR and solid feeds, as well as blood metabolites in dairy calves. Upon 24 to 96 h after birth, 63 calves were acquired from dairy farms and incorporated into the study. Calves were blocked based on arrival day and randomly assigned within each block to one of 3 treatments differing in MR fat composition (n = 21 per group): VG was based on vegetable fats including 80% rapeseed and 20% coconut fats; AN was formulated with animal fats including 65% lard and 35% dairy cream; and MX with a mixture of 80% lard and 20% coconut fats. All 3 MR contained 30% fat, 24% crude protein, and 36% lactose and were formulated to have a fatty acid profile resembling that of milk fat. From arrival onward (3.1 ± 0.84 d of age; means ± standard deviation), calves were group housed and were offered an ad libitum supply of MR at 135 g/L (13.5% solids). Weaning was gradual and induced between wk 7 and 10, after which calves were fed only solid feeds. Starter feed, chopped straw, and water were offered ad libitum throughout the study. Calves were weighed, and blood was collected weekly until d 84 after arrival. Preweaning average daily gain was greater in calves fed AN (915 g/d) than other treatments (783 g/d), whereas no differences were detected in the weaning and postweaning phases. Preweaning MR intake was greater in calves fed AN than MX from wk 2 to 6 and was also higher in calves fed AN than VG in wk 5 and 6. Consistently, the number of rewarded visits during the ad libitum phase was greater in calves fed AN than MX, whereas VG showed no differences. This led to a higher preweaning total metabolizable energy intake in calves fed AN than in calves fed VG and MX. Serum cholesterol was higher, and serum albumin was lower in calves fed VG than other treatments. The proportion of high-density lipoprotein cholesterol in total plasma cholesterol was lower and that of low-density lipoprotein (LDL) cholesterol was higher in calves fed VG compared with other treatments. Overall, the fatty acid profile of plasma largely mirrored the MR fat composition during the preweaning period. Feeding AN enhanced MR intake and improved preweaning growth compared with other treatments. Feeding VG resulted in a marked increase in plasma cholesterol, particularly in the form of LDL cholesterol, which could be linked to an excessive intake of polyunsaturated fatty acids. These findings underscore the importance of formulating the fat content of MR to be similar to bovine milk fat.

Fat composition of milk replacer influences postprandial and oxidative metabolisms in dairy calves fed twice daily

Milk replacers (MR) for calves contain alternative fat sources as substitute for milk fat. This substitution leads to differences in fat properties, such as the fatty acid profile and the triglyceride structure. This study evaluated how fat composition in MR affects gastrointestinal health, blood redox parameters, and postprandial metabolism in calves fed twice daily. Forty-five individually housed male Holstein-Friesian calves (2.3 ± 0.85 d of age) were assigned to 1 of 15 blocks based on the age and the day of arrival. Within each block, calves were randomly assigned to 1 of 3 experimental diets and received their respective diet from arrival until 35 d after arrival. The 3 experimental diets (n = 15 per treatment group) consisted of an MR with a blend of vegetable fats containing rapeseed and coconut (VG), an MR with only animal fats from lard and dairy cream (AN), and an MR containing a mixture of animal and vegetable fats including lard and coconut (MX). The fatty acid profile of each MR was formulated to resemble that of bovine milk fat while using only 2 fat sources. All MR were isoenergetic, with 30% fat (% DM), 24% crude protein, and 36% lactose. Chopped straw and water were available ad libitum from arrival onward but no starter feed was provided. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 135 g/L (13.5% solids). Fecal appearance was scored daily; calves were weighed and blood was drawn on arrival and weekly thereafter. Urine and feces were collected over a 24-h period at wk 3 and 5 to determine apparent total-tract digestibility and assess gastrointestinal permeability using indigestible markers. Postprandial metabolism was evaluated at wk 4 by sequential blood sampling over 7.5 h, and the abomasal emptying rate was determined by acetaminophen appearance in blood. Fat composition in MR did not affect growth, MR intake, gastrointestinal permeability, nor nutrient digestibility. The percentage of calves with abnormal fecal scores was lower at wk 2 after arrival in calves fed VG than MX, whereas AN did not differ from the other treatments. Calves fed AN and MX had higher thiobarbituric acid reactive substances measured in serum than VG, whereas plasma ferric-reducing ability was greater in calves fed MX than VG. Postprandial acetaminophen concentrations did not differ across treatment groups, but the area under the curve was smaller in calves fed VG than in the other 2 treatments, which is indicative of a slower abomasal emptying. Postprandial serum triglyceride concentration was greater in calves fed AN than VG, whereas MX did not differ from the other treatments. Based on these outcomes, all 3 fat blends can be considered suitable for inclusion in MR for calves.

Postnatal Growth and Development of the Rumen: Integrating Physiological and Molecular Insights

The rumen plays an essential role in the physiology and production of agriculturally important ruminants such as cattle. Functions of the rumen include fermentation, absorption, metabolism, and protection. Cattle are, however, not born with a functional rumen, and the rumen undergoes considerable changes in size, histology, physiology, and transcriptome from birth to adulthood. In this review, we discuss these changes in detail, the factors that affect these changes, and the potential molecular and cellular mechanisms that mediate these changes. The introduction of solid feed to the rumen is essential for rumen growth and functional development in post-weaning calves. Increasing evidence suggests that solid feed stimulates rumen growth and functional development through butyric acid and other volatile fatty acids (VFAs) produced by microbial fermentation of feed in the rumen and that VFAs stimulate rumen growth and functional development through hormones such as insulin and insulin-like growth factor I (IGF-I) or through direct actions on energy production, chromatin modification, and gene expression. Given the role of the rumen in ruminant physiology and performance, it is important to further study the cellular, molecular, genomic, and epigenomic mechanisms that control rumen growth and development in postnatal ruminants. A better understanding of these mechanisms could lead to the development of novel strategies to enhance the growth and development of the rumen and thereby the productivity and health of cattle and other agriculturally important ruminants.

A Comprehensive Review of Bovine Colostrum Components and Selected Aspects Regarding Their Impact on Neonatal Calf Physiology

Colostrum contains macro- and micronutrients necessary to meet the nutritional and energy requirements of the neonatal calf, bioactive components that intervene in several physiological aspects, and cells and microorganisms that modulate the calf's immune system and gut microbiome. Colostrum is sometimes mistaken as transition milk, which, although more nutritive than whole milk, has a distinct biochemical composition. Furthermore, most research about colostrum quality and colostrum management focuses on the transfer of maternal IgG to the newborn calf. The remaining components of colostrum and transition milk have not received the same attention, despite their importance to the newborn animal. In this narrative review, a large body of literature on the components of bovine colostrum was reviewed. The variability of these components was summarized, emphasizing specific components that warrant deeper exploration. In addition, the effects of each component present in colostrum and transition milk on several key physiological aspects of the newborn calf are discussed.

Modulating Gastrointestinal Microbiota in Preweaning Dairy Calves: Dose-Dependent Effects of Milk-Based Sodium Butyrate Supplementation

Sodium butyrate (SB), an essential nutritional additive for livestock, has drawn notable interest for its potential for enhancing microbiota development in ruminant animals. This study aimed to assess SB's effects on ruminal and intestinal microbiota when added to milk for preweaning dairy calves nearing 45 days old. We administered SB in the calves' milk at four levels: 0 g/d (control), 4.4 g/d (low), 8.8 g/d (medium), and 17.6 g/d (high). After a six-week trial with ten replicates per group, ruminal fluid and fecal samples were collected for 16S rRNA sequencing, specifically targeting the V3-V4 regions to analyze microbiota. The results indicated an enhancement in ruminal microbiota, particularly in community richness, with low-level SB supplementation but minimal benefits from medium and high levels of supplementation. Increasing the level of SB supplementation had a negative impact on intestinal microbiota, affecting community richness and some potentially beneficial bacterial genera. However, low SB supplementation could positively adjust the communication between ruminal and intestinal microbiota. Overall, this study suggests feeding milk supplemented with a low level of SB to suckling calves close to an older age to promote ruminal microbiota development.

Initial timing of alfalfa hay supplementation manipulates blood parameters, rumen gene expression, and epithelial microbiota in pre-weaning lambs

The present study aimed to investigate the impact of initiating alfalfa supplementation at either 14 d or 42 d of age on growth performance, blood parameters, rumen tissue gene expression, and epithelial microbiota in pre-weaning lambs. A total of 42 seven-day-old male Hu lambs (3.88 ± 0.92 kg) were selected for this study. After 7 d of adjustment period, 6 lambs were slaughtered at 14 d of age to establish a baseline control. The remaining 36 lambs were randomly allocated to 2 treatment groups, every 3 lambs were considered a unit, including fed milk replacer, starter pellets, and either alfalfa hay fed at 14 (EAF) or 42 d of age (LAF). Body weight and feed intake were recorded for lamb until 70 d of age. Blood samples, rumen tissue samples, and epithelial microbiota samples were collected from the lambs at 42, 56, and 70 d of age. The results indicated that average daily gain, starter intake, and total dry matter intake were greater in the EAF group compared to the LAF group from 14 to 42 d of age (P < 0.01), but no significant differences from 43 to 70 d of age or during the entire trial. Treatment and age interactively affected the alfalfa intake (P = 0.02) from 43 to 70 d of age. The concentration of serum immunoglobulin A (IgA) (P < 0.01) and the expression of the rumen gene insulin-like growth factor-1 (P < 0.01) were greater in the EAF group compared to the LAF group at 42 d of age. Furthermore, the concentrations of alkaline phosphatase (P = 0.03), albumin (P < 0.01), total protein (P = 0.03), urea (P = 0.04), lipopolysaccharide (P < 0.01), β-hydroxybutyric acid (P = 0.02), interleukin-1β (IL-1β) (P < 0.01), IL-4 (P < 0.01), and tumor necrosis factor-α (P < 0.01) were affected by age. The abundance of Prevotella was lower (P < 0.05), whereas Megasphaera (P < 0.05) was greater in the EAF group compared to the LAF group at 42 d of age. The early addition of alfalfa promotes rumen epithelial microbiota colonization. In conclusion, this study demonstrated that alfalfa provision at 14 d of age promotes growth performance in lambs, but this effect disappeared at 43 to 70 d of age. Moreover, provision of alfalfa at 14 d of age enhances the immune response, promotes rumen tissue cell proliferation, and affects dynamical changes of rumen epithelial microbiota. Meanwhile, our findings showed that the rumen undergoes significant physiological challenges during the transition from a liquid diet to a solid diet.

Effects of oral or parenteral iron supplementation on haematological parameters, blood iron status and growth in newborn calves fed milk replacer

BACKGROUND

This study aimed to assess the influence of early life iron supplementation on the haematological parameters of calves fed milk replacer on a high plane of nutrition.

METHODS

Thirty calves were allocated to receive either a sham treatment (CON), injection of 1000 mg Fe3+ (INJ) or oral administration of 1050 mg Fe3+ (ORAL), all administered less than 1 hour after birth. Blood was obtained before treatment, on days 1, 3, 5 and 7 of life and once weekly until week 9. Samples were analysed for haemoglobin (Hb), packed cell volume (PCV) and estimated transferrin saturation (%TSAT).

RESULTS

The Hb and PCV of calves in the INJ and ORAL groups were above the values of those in the CON group throughout the study. Hb and PCV of the CON group remained within the reference range for calves. The %TSAT exceeded reported ranges in the ORAL group in the first week. Values for the CON group were below the INJ and ORAL groups throughout the entire study. Average daily gain did not differ between treatments.

LIMITATIONS

The sample size was insufficient to assess the influence of iron supplementation on disease development. Furthermore, the study was set in a controlled environment and not performed under field conditions.

CONCLUSIONS

Oral and subcutaneous iron administration had similar effects on haematological development but resulted in numerically different transferrin saturation. Control animals showed lower Hb and PCV but did not develop overt anaemia.

Butyrate supplementation in the liquid diet of dairy calves leads to a rapid recovery from diarrhea and reduces its occurrence and relapses in the preweaning period

The present study aimed to evaluate the effect of continuous butyrate administration in dairy calves' liquid diet considering diarrhea, metabolic profile, gastrointestinal development, and corporal growth. Immediately after birth, calves were randomly allocated into 2 groups of 62 calves (50 females and 12 males), with access to water and a solid feed ad libitum. The butyrate group (BG) received 4 g/d of sodium butyrate (Admix Easy, Adisseo) diluted in the whole milk, and the control group (CG) received whole milk with no supplementation. Sodium butyrate was administered from d 1 of life until the weaning at 90 d. Feces consistency was assessed daily for the first 30 d of life and characterized by scores from 0 to 4 (0 and 1 for normal, and 2, 3, and 4 for abnormal feces). Diarrhea was diagnosed when the animals had abnormal feces and fever. Morbidity, recurrence, mortality, and lethality data were recorded and compared between the groups. Average daily gain (ADG) and corporal growth (body weight, thoracic perimeter, height at the withers, and croup width) were evaluated weekly, from the first day to d 30, and later at 45, 60, and 90 d of life. Blood samples were taken weekly for up to 30 d to determine the circulating levels of total calcium, phosphorus, chloride, bicarbonate, glucose, β-hydroxybutyrate, and nonesterified fatty acids. The males were euthanized at 15 (n = 6 per group) and 30 d (n = 6 per group) for morphometric, histological, and gene expression analysis of the gastrointestinal tract. The results showed that the BG had a lower rate of morbidity (BG = 30% vs. CG = 50%) and recurrence (BG = 26.7% vs. CG = 60%) of diarrhea than the CG. In addition, the BG had abnormal feces for a shorter period (BG = 4.64 ± 0.47 d vs. CG = 8.6 ± 0.65 d). The ADG tended to be higher in BG than CG up to 30 and 60 d. Metabolic evaluations showed the lowest levels of glucose and highest levels of nonesterified fatty acids in BG. On d 30 of life, rumen papillae length, papilla area, duodenum villus length, and crypt depth were higher in BG than in CG. The duodenal gene expression at 30 d showed that animals with diarrhea episodes that did not receive butyrate had the highest levels of transcripts for the LCT and GLP2 genes. In addition, in different ways, both butyrate and neonatal diarrhea affected the gene expression of IGF1, SLC5A1, and AQP3. These results allow us to conclude that continuous supplementation with sodium butyrate improves gastrointestinal development, reduces the occurrence of diarrhea, and makes clinical conditions milder with faster recovery, favoring a higher ADG in the first 30 and 60 d of life. Based on these results, we conclude that sodium butyrate can be indicated for liquid diet supplementation to accelerate gastrointestinal tract development and prevent severe cases of neonatal diarrhea, tending to improve average daily gain until weaning.

Benefits of barley straw as a forage for dairy calves before and after weaning

The aim of this study was to assess the potential consequences on calf intake, performance, behavior, ruminal microbiome, and ruminal epithelium development of combining the inclusion of chopped barley straw and alfalfa hay during the pre- and postweaning periods keeping concentrate to forage ratio constant among dietary treatments. Forty-five Holstein calves (44 ± 5.7 kg of body weight [BW] and 3 ± 1.5 d of age) individually penned were blocked by BW and randomly assigned to a common pellet concentrate fed ad libitum along with one of following forage feeding strategies: barley straw before and after weaning (S-S), barley straw before and alfalfa hay after weaning (S-A), or alfalfa hay before and after weaning (A-A). All calves received the same milk replacer regimen. Forage was supplied in a separated bucket at the rate of 7.5% (preweaning) and 15% (postweaning) of total solid feed intake of the previous day. Feed intake and BW were recorded daily and weekly, respectively. Rumen samples were obtained via a stomach tube at 53, 66, and 87 d and were composite in 3 samples of 5 animals each for subsequent rumen microbiome analysis. A rumen epithelium sample was taken by endoscopy at 90 d to assess gene expression of OCLN, CLDN4, SLC9A1, SLC9A3, SLC16A1, SLC16A4, IL6, and TGFB1. Data were analyzed with a mixed-effects model accounting for the fixed effects of block, forage, week of study, and their interaction, and calf as a random effect. The type of forage fed did not affect concentrate feed, forage, or total DM intake before weaning. However, S-A and A-A calves consumed less concentrate feed and S-A calves grew at a lower rate after weaning than S-S calves. Expression of the gene coding for SLC16A1 in the rumen epithelium was greatest in S-S among treatments. Rumen microbiome did not differ among treatments, while the relative abundance of Acidaminococcus and Selenomas genera increased, while Alloprevotella, Bifidobaterium, Olsenella, and Succiclasticum genera decreased with age. In conclusion, feeding barley straw before and after weaning was more effective than feeding alfalfa hay in promoting concentrate feed intake after weaning and fostering an increase in the expression of SLC16A1 in the rumen epithelium.

Effects of fat source in calf starter on growth performance, blood fatty acid profiles, and inflammatory markers during cold season

This study was conducted to investigate the effects of supplementation of different fat sources in calf starters on growth performance, health, blood fatty acid profiles, and inflammatory markers during the cold season in dairy calves. A total of 48 Holstein calves (24 males and 24 females) were randomly assigned to 1 of 4 starter diets throughout the experiment (d 3 to 65): (1) no supplemented fat (CON), (2) 3% calcium-salts of soybean oil (Ca-SBO), (3) 3% calcium-salts of fish oil (Ca-FO), and (4) 3% mixture of Ca-SBO and Ca-FO (1.5% each, DM basis; MIX). Calves were given free access to starter feed and water and were raised individually in pens from 3 to 65 d of age. Calves fed Ca-SBO consumed a greater proportion of n-6 FA, while calves fed Ca-FO consumed a greater level of n-3 FA compared to the other dietary treatments. Fat supplementation increased the intake of linoleic acid, the major n-6 FA, with the greater intake observed in the Ca-SBO group compared to the other dietary treatments. Calves fed the Ca-FO and MIX diets consumed more long-chain n-3 FA than the other diets. In addition, calves fed Ca-SBO and Ca-FO diets consumed more starter feed and total dry matter than calves fed MIX and CON throughout the experiment (d 3 to 65). Calves fed Ca-FO had higher average daily gain throughout the trial (d 3 to 65) than the other treatment groups. Of all treatment groups, calves fed Ca-FO achieved the highest final body weight and showed the greatest feed efficiency. Random forest analysis revealed that eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid were the serum levels of FA most affected by the diets. The principal component analysis of blood FA profile, blood parameters, and inflammatory markers showed distinct differences between dietary treatments. Calves fed Ca-SBO had higher plasma concentrations of linoleic acid, while calves fed Ca-FO had higher plasma concentrations of long-chain n-3 polyunsaturated fatty acids (PUFA), such as EPA, docosapentaenoic acid (DPA), and DHA than the other treatment groups. Plasma inflammatory markers were lower in calves fed Ca-FO and higher in calves fed CON than in the other treatment groups. The Ca-FO group had lower levels of inflammatory markers, including serum amyloid A, tumor necrosis factor-alpha, Interferon-γ, haptoglobin, and interleukin-6 compared to the other experimental treatments. Also, the blood malondialdehyde levels, an indicator of oxidative stress, were lower in calves fed Ca-FO compared with calves fed the other treatment diets. In conclusion, the performance of preweaned dairy calves can be improved by adding fat to their starter feed under cold conditions. Overall, the type of fat in milk may affect growth and inflammation of dairy calves before weaning under cold conditions, with n-3 FA (Ca-FO) promoting growth and reducing inflammation more effectively than n-6 FA (Ca-SBO).

Essential oil blend supplementation in the milk replacer of dairy calves: Performance and health

Supplementation of dairy calves with essential oils in the liquid diet can reduce the incidence and severity of infectious diseases and promote better performance. Our objective was to evaluate an essential oil blend containing peppermint, eucalyptus, and menthol crystals and its effect on performance and health during the pre and postweaning period of dairy calves. At birth, 40 dairy calves (34 males and 6 females) were blocked according to sex and birth weight, randomly assigned to one of two treatments-commercial milk replacer diluted at 14% (MR) and the same liquid diet plus essential oil blend (MREO) at a dose of 4 mL per calf per day, divided into two meals during the first 28 days of life. Calves were individually housed and fed 6 L/d of the liquid diet, divided into two meals, and received starter concentrate and water ad libitum. Weaning was gradually reduced by 1L per day at d 51 until complete weaning at 56 days. After weaning, calves were evaluated until 70 days of age, when the experimental period ended. Intake, fecal, and health scores were evaluated daily, weight and body measures were recorded weekly, and blood parameters were evaluated at weeks 1, 2, 3, 4, and 8. Calves fed MREO tended to have higher total dry matter intake during the preweaning period. Furthermore, MREO calves had lower health scores and fewer days with a health score ≥ 4 (suggestive of bronchopneumonia), tended to lower coughing days and fewer veterinary interventions preweaning, and tended to lower health scores postweaning. The supplementation with a blend of essential oils containing peppermint, eucalyptus, and menthol crystals can reduce respiratory problems. Further studies are needed to investigate the dose and the supplementation period.

Effects of dietary extrusion on rumen fermentation, nutrient digestibility, performance and milk composition of dairy cattle: a meta-analysis

OBJECTIVE

The present study aimed to evaluate the effects of extruded and unextruded feeding on the performance, milk composition, digestibility and ruminal fermentation of dairy cows through a meta-analysis.

METHODS

The database was compiled from 53 studies in Scopus and PubMed. The data were analyzed using a random effects model in OpenMEE software. Extruded feed was grouped as the experiment group while and the others as control group. The bias of publication in the main parameter of dairy performance was evaluated by a funnel plot.

RESULTS

The result showed that extruded feed enhanced the milk yield, dry matter and crude protein digestibility, butyrate and valerate acid production (p<0.05). Meanwhile, the extruded feed significantly decreased the milk fat and protein concentration (p<0.05). Also, the iso-butyrate and iso-valerate in unextruded feeding was significantly higher than the extruded feed (p<0.05).

CONCLUSION

It was concluded from the meta-analysis that extruded feed effectively improved the milk production and milk lactose concentration, dry matter and protein digestibility, but not the milk fat and protein concentration.

Invited review: The effect of milk feeding practices on dairy calf behavior, health, and performance-A systematic review

The aim of this systematic review was to summarize the literature assessing the effects of milk feeding practices on behavior, health, and performance on dairy calves. Peer-reviewed, published articles, written in English, directly comparing the effects of milk allowance, milk feeding methods, or milk feeding frequency on dairy calves were eligible for inclusion. Outcome measures could include sucking behavior, sucking on a teat (nutritive sucking, non-nutritive sucking on a teat), abnormal sucking behavior (non-nutritive sucking on pen fixtures, other oral behaviors, or cross-sucking), signs of hunger (vocalizations or unrewarded visits at the milk feeder), activity (lying time or locomotor play), feeding behavior (milk intake, starter intake, milk meal duration, or starter meal duration), growth (body weight or average daily gain), and health (occurrence of diarrhea, respiratory disease, or mortality). We conducted 2 targeted searches using Web of Science and PubMed to identify key literature. The resulting articles underwent a 2-step screening process. This process resulted in a final sample of 94 studies. The majority of studies investigated milk allowance (n = 69). Feeding higher milk allowances had a positive or desirable effect on growth, reduced signs of hunger, and increased locomotor play behavior during the preweaning period, whereas starter intake was reduced. Studies addressing health pointed to no effect of milk allowance, with no consistent evidence indicating that higher milk allowances result in diarrhea. Studies addressing milk feeding methods (n = 14) found that feeding milk by teat reduced cross-sucking and other abnormal oral behaviors. However, results on the effect of access to a dry teat were few and mixed. Milk feeding frequency (n = 14 studies) appeared to have little effect on feed intakes and growth; however, there is some evidence that calves with lower feeding frequency experience hunger. Overall, findings strongly suggest feeding higher volumes of milk using a teat; however, further work is needed to determine the optimal feeding frequency for dairy calves.

Effect of pH and lipopolysaccharide on tight junction regulators and inflammatory markers in intestinal cells as an experimental model of weaning transition in dairy calves

Acidic conditions combined with the presence of lipopolysaccharide (LPS) may increase the permeability of gastrointestinal epithelium. Feeding starch-rich starter to dairy calves is associated with ruminal acidosis and decreases the pH of other segments of the gastrointestinal tract, and that affects the tight junction regulator. The objective was to evaluate the effect of the combination of different pH (7.4 vs. 6.0) and LPS concentrations (0, 0.5, 10 ng/mL) in intestinal cells on tight junction regulators, inflammatory markers, and permeability. The human colon carcinoma Caco-2 cell line was used with the main treatment of pH and LPS in a 2 × 3 factorial arrangement. The pH was acidic (pH 6.0) or physiologic (pH 7.4), whereas LPS was 0, 0.5, or 10 ng/mL. After cells reached 70%-80% of confluence, the media were replaced with each respective treatment medium. Cells were treated for 3 h for mRNA abundance analysis, 3 and 6 h for protein abundance determination, and 3, 6, 12, and 24 h for permeability determination. Protein abundance of the myosin light-chain kinase (MYLK) and toll-like receptor 4 (TLR4) were measured by western blot. The mRNA abundance of IL-8, MYLK, peroxisome proliferator activated receptor gamma, and nuclear factor kappa B (Nfkb1) was determined by real-time, quantitative PCR. Paracellular permeability was determined with Lucifer yellow after 21 d of incubation. Cell culture was performed in biological triplicate; each biological replicate for real-time, quantitative PCR had 2 technical replicates, and for protein abundance and permeability assay had one technical replicate. The MIXED procedure of SAS (SAS Institute Inc.) was used with LPS, pH, and pH × LPS as fixed effects. Significance was declared at P ≤ 0.05 and tendencies when 0.05 < P ≤ 0.10. Increasing LPS doses did not affect the protein abundance of MYLK and TLR4, nor mRNA abundance of MYLK and PPRG. The LPS tended to increase mRNA abundance of IL-8 while pH × LPS interactively increased mRNA abundance of Nfkb1, where mRNA abundance of Nfkb1 was lower in cells exposed to pH 6.0 when combined with 0 and 10 ng/mL of LPS. Contrary to expectations, LPS did not affect the permeability of Caco-2 cells. The mRNA abundance of MYLK was greater at pH 6.0 versus pH 7.4. Also, protein abundance of TLR4 was lower at pH 6.0 than pH 7.4, and it decreased when exposure increased to 6 h. In addition, mRNA abundance of IL-8 was lower at pH 6.0 versus pH 7.4. Permeability was greater at pH 6.0 versus 7.4 after 6, 12, and 24 h of treatment. In summary, the effect of LPS and its interaction with pH showed less impact than expected on dependent variables measured, which might be attributed to the adopted clinically achievable LPS doses likely not being high enough to draw a strong response as observed in the literature. On the other hand, pH was far more relevant, modulating mRNA abundance of inflammatory markers, tight junction regulators, and permeability in in vitro colon cell models.

The age at first consumption of forage in calves and its effect on growth and rumination in the short- and long-term

BACKGROUND

Previous investigations into the effect of dietary forage on calf performance have been inconsistent, and there is a paucity of information exploring the effect of age on the growth performance and rumination of calves. Eighty-four female Holstein calves (41.5 ± 4.2 kg) were enrolled at birth, a subset of the calves were fed calf starter only (CON, n = 21) while the rest (n = 63) were classified into three treatment groups: the early (EHAY, n = 26, 5.1 ± 0.8 d), the middle (MHAY, n = 21, 7.9 ± 0.8 d) and the late (LHAY, n = 16, 12.1 ± 1.4 d) hay consumers. The short-term effect of the age at first forage consumption (AFF) on calves' feed intake was monitored until d 84. In addition, the long-term effects of AFF on body weight, structural growth and rumination behavior were recorded until d 196. Rumen samples were collected on d 1, 7, 35, 84 and 196 to analyze the rumen fermentation, while fecal samples were collected from d 78 to 84 to estimate digestibility parameters.

RESULTS

Treatment had no effect on feed intake. While, the EHAY calves tended to have lower BW and ADG compared to LHAY and CON calves. Several total-tract apparent digestibility parameters and digestible nutrients intake were significantly lower in EHAY calves compared with CON and LHAY calves. Calves in the EHAY group tended to begin ruminating ealier, while CON calves were the latest (12.3 vs. 15.5 days of age). A treatment and time interaction was present for rumination time due to greater rumination in calves consuming hay compared to CON calves in week 10 to 12, the differences in rumination disappeared afterwards, no long-lasting significant differences in the rumination and rumen fermentation parameters were found between treatments.

CONCLUSIONS

In conclusion, this study showed that hay consumption earlier in life (in the first week, around 5 days of life) could negatively affect the growth of the calf in the short and long term. Compared to consuming hay from the second week (around 12 days of life) or feeding concentrate only without hay, starting to consume hay from the first week could compromise nutrient digestibility and digestible nutrient intake independent of developing rumination behaviour and rumen fermentation.

Effects of Sodium Butyrate Supplementation in Milk on the Growth Performance and Intestinal Microbiota of Preweaning Holstein Calves

The aim of the present study was to investigate the effects of sodium butyrate (SB) supplementation on the growth and intestinal microbiota of preweaning dairy calves. Eighty newborn Holstein calves (56 female and 24 male) were randomly allocated to four treatment groups with 20 calves each (14 female and 6 male). The suckling milk for the four treatments was supplemented with 0, 4.4, 8.8, or 17.6 g/d SB. During the 6-week experiment, dry matter intake was recorded daily, body weight was measured weekly, and rectal fecal samples were collected in the 2nd week. The V3-V4 hypervariable regions of the microbial 16S rRNA were amplified and then sequenced. SB supplementation elevated average daily gains (ADGs) in the first and second weeks. The optimal SB supplementation level for the whole preweaning period was 8.78 g/d, as revealed by analyzing the whole preweaning period ADG using second-order polynomial regression (quadratic) equations. The alpha diversity (Shannon diversity index), beta diversity, core phyla and genera, and function of the intestinal microbiota were affected by SB supplementation. In addition, the Shannon diversity index and core phyla and genera of the intestinal microbiota were correlated with calf growth-related indices. Overall, SB supplementation in suckling milk improved the growth performance and intestinal microbiota development of dairy calves in a quadratic manner, and regression analysis indicated an optimal supplementation level of 8.78 g/d.

Effect of kraft pulp inclusion in calf starter on performance, health, and plasma concentration of glucagon-like peptide 2 in calves

Kraft pulp (KP), an intermediate product obtained when wood chips are converted to paper, contains highly digestible fiber. This study evaluated the effect of KP inclusion in calf starters on growth performance, health, and plasma glucagon-like peptide 2 (GLP-2) concentration in calves. Twenty-five Holstein heifer calves were raised on a high plane of nutrition program using milk replacer containing 29% crude protein and 18% fat until 49 d after birth, and were fed calf starters containing KP at 0 (CON; n = 14) or 12% (KPS; n = 11) on a dry matter basis. All calves were fed the treatment calf starters and timothy hay ad libitum. Blood was collected at 4, 14, 21, 35, 49, 70, and 91 d after birth. Dry matter intake (DMI) of milk replacer and hay was not affected by treatment, whereas calf starter DMI was lower for KPS (0.93 kg/d) than for CON (1.03 kg/d). Higher neutral detergent fiber (NDF) content in KPS (31.7%) than in the CON starter (22.1%) resulted in higher NDF intake for KPS (0.55 kg/d) than for CON (0.47 kg/d). However, the consumption of starch was lower for KPS (0.29 kg/d) than for CON (0.33 kg/d). Despite the lower starter intake for KPS, body weight and average daily gain did not differ between treatments. No significant difference was observed in the plasma concentrations of metabolites, except for β-hydroxybutyrate (BHB); BHB concentration was lower for KPS (216 μmol/L) than for CON (257 μmol/L). The area under the curve for plasma GLP-2 concentration was higher for KPS (54.1 ng/mL × d) than for CON (36.0 ng/mL × d). Additionally, the fecal score postweaning (1.19 and 1.48 for KPS and CON, respectively) and the number of days that calves developed diarrhea throughout the experimental period (2.50 d and 8.10 d for KPS and CON, respectively) were lower for KPS than for CON. These results indicate that feeding KP reduces the severity and frequency of diarrhea without adversely affecting growth performance. This could be attributed to the increased plasma GLP-2 concentration induced by higher NDF intake.

Providing long hay in a novel pipe feeder or a bucket reduces abnormal oral behaviors in milk-fed dairy calves

Many milk-fed dairy calves are not provided forage. In these settings, calves often perform abnormal repetitive behaviors (ARBs), including tongue rolling and nonnutritive oral manipulation (NNOM), which, based on their form, seem similar to movements used when processing feed. Feeding hay, typically presented as a short chop (≤5 cm) in a bucket, reduces ARBs. Our objective was to evaluate whether altering the presentation method of long hay (∼19 cm), by providing it in a bucket or a novel polyvinyl chloride (PVC) pipe feeder, could reduce ARBs. Holstein heifer calves were housed individually on sand and fed ad libitum starter grain and limited milk replacer (5.7-8.4 L/d step-up) via a bottle (Control, n = 9) or given access to mountaingrass hay in a bucket (Bucket, n = 9) or in a PVC pipe feeder (Pipe, n = 9). The 56 × 10.2 cm (length × diameter) PVC pipe feeder had 4 openings that were 6.35 cm wide, which required the calf to insert her tongue into the pipe and curl her tongue to extract hay. Treatments were applied from birth through 50 d of age, when step-down weaning began and TMR was provided to all calves. Calves were fully weaned at d 60. At wk 4 and 6, oral behaviors (eating, ruminating, drinking water, sucking milk, self-grooming, NNOM, tongue rolling, tongue flicking, and panting) were recorded by direct observation for 24 h using 1-0 sampling during 5-s intervals. Feeding long hay, regardless of presentation method, increased overall DMI, grain intake, and ADG compared with Control calves. Hay provision also increased rumination (25 vs. 15% of 24-h observations in Control) and eating time (5.5 vs. 2% in Control). Abnormal behaviors were seen in all calves. Hay provision reduced some of these, including NNOM (5 vs. 9% in Control). There was no difference in NNOM between calves fed hay in a pipe or bucket, even though Bucket calves consumed more hay (178 vs. 129 g/d in wk 6) and tended to spend more observations eating hay than Pipe calves (4.5 vs. 3%). Hay provision did not affect other behaviors: drinking water (0.5%), grooming (3%), or tongue flicking (3%). We also found evidence of other abnormal oral behaviors that have received less attention. Calves showed signs of polydipsia, and displayed excessive grooming, the latter indicated by overall duration, number of bouts per day, and duration of individual bouts (up to 25 min). Tongue rolling was expressed at low levels (up to 0.4% of intervals) but by 85% of calves. Feeding hay, both in a bucket and using novel methods, was not enough to counteract the welfare challenges associated with individual housing and limited ability to suck milk (<1% of time). Provision of long hay, regardless of presentation method, promotes rumination, improves performance (higher grain intake and ADG) and reduces at least some, but not all, of the considerable abnormal oral behaviors these calves performed.

Early Supplementation with Starter Can Improve Production Performance of Lambs but this Growth Advantage Disappears after 154 Days of Age

The aim of this experiment was to study the sustained effects of early supplementation with a starter on the performance of lambs during the pre-weaning, post-weaning, and fattening periods. Sixty male Hu lambs (3.59 ± 0.05 kg) were randomly assigned to two (30 lambs per group) treatments. The lambs were fed milk replacer from three days of age. The early supplementation (ES) group was supplemented with a starter ration at seven days of age, the control (CON) group was supplemented at 21 days of age, and lambs in both groups were weaned from milk replacer at 28 days of age. Eight lambs from each group were randomly slaughtered at 98 days of age, and the remaining lambs were fed the same nutrient level of a fattening ration until slaughter at 200 days of age. The results showed that early supplementation with starter significantly improved average daily feed intake (ADFI) and average daily weight gain (ADG) in the pre-weaning period (7-28 days of age), and ADFI and slaughter performance (live weight before slaughter, carcass weight and dressing percentage) in the post-weaning period (29-98 days of age, p < 0.05). In addition, early supplementation with the starter had no significant effect (p > 0.05) on ADFI, ADG, and slaughter performance, but significantly decreased (p < 0.05) the feed-to-gain ratio (F/G) of lambs during the fattening period (99-200 days of age). In addition, early supplementation with starter increased the ratio of rumen and reticulum weight to total stomach weight in lambs (p < 0.05). In conclusion, early supplementation with starter can reduce feed costs and improve the performance of lambs, while the growth advantage produced by early supplementation had initially disappeared by 154 days of age.

Relationship between hindgut microbes and feed conversion ratio in Hu sheep and microbial longitudinal development

Feed efficiency is an important indicator in the sheep production process, which plays an important role in improving economic benefits and strengthening energy conservation and emission reduction. Compared with the rumen, the fermentation of the hindgut microorganisms can also provide part of the energy for the host, and the composition of the hindgut microorganisms will affect the feed efficiency. Therefore, we hope to find new ways to regulate sheep feed efficiency by studying the sheep gut microbes. In this study, male Hu sheep with the same birth date were raised under the same conditions until 180 d old. The sheep were divided into high and low groups according to the feed conversion ratio (FCR) at 80 to 180 d old, and the differences in rectal microorganisms between the two groups were compared. The permutational multivariate analysis (PERMANOVA) test showed that there were differences in microorganisms between the two groups (P < 0.05). Combined with linear fitting analysis, a total of six biomarkers were identified, including Ruminobacter, Eubacterium_xylanophilum_group, Romboutsia, etc. Functional enrichment analysis showed that microorganisms may affect FCR through volatile fatty acids synthesis and inflammatory response. At the same time, we conducted a longitudinal analysis of the hindgut microbes, sampling nine-time points throughout the sheep birth to market stages. The microbiota is clearly divided into two parts: before weaning and after weaning, and after weaning microbes are less affected by before weaning microbial composition.

An Evaluation of Nutritional and Therapeutic Factors Affecting Pre-Weaned Calf Health and Welfare, and Direct-Fed Microbials as a Potential Alternative for Promoting Performance—A Review

The priority for calf rearing has been to maintain good health and welfare in order to promote and sustain future production. However, there have been numerous reports of undesirable levels of morbidity and mortality amongst pre-weaned calves. This may be mitigated or exacerbated by nutritional management practices. Some areas of concern include colostrum feeding, utilization of waste milk, and restrictive milk feeding regimes. Antibiotics may be prescribed at lethal or sub-inhibitory doses to treat or prevent disease. However, extensive antibiotic use may disrupt the gastrointestinal microbiota and aid in expanding the antibiotic resistant gene pool. In an attempt to reduce the use of antibiotics, there is a demand to find alternative performance enhancers. Direct-fed microbials, also known as probiotics, may comply with this role. A DFM consists of live microorganisms that are biologically active and able to confer health benefits onto the host. Lactic acid bacteria have been the most frequently investigated; however, this field of research has expanded to include spore-forming bacteria and live yeast preparations. This review aims to provide a comprehensive evaluation of the nutritional management strategies that may increase a calf’s susceptibility to morbidity and mortality, the efficacy and sustainability of antibiotics as a tool for managing calf health and welfare, and the potential for DFMs as a supportive strategy for promoting calf wellbeing.

Welfare of cattle during transport

In the framework of its Farm to Fork Strategy, the Commission is undertaking a comprehensive evaluation of the animal welfare legislation. The present Opinion deals with protection of cattle (including calves) during transport. Welfare of cattle during transport by road is the main focus, but other means of transport are also covered. Current practices related to transport of cattle during the different stages (preparation, loading/unloading, transit and journey breaks) are described. Overall, 11 welfare consequences were identified as being highly relevant for the welfare of cattle during transport based on severity, duration and frequency of occurrence: group stress, handling stress, heat stress, injuries, motion stress, prolonged hunger, prolonged thirst, respiratory disorders, restriction of movement, resting problems and sensory overstimulation. These welfare consequences and their animal-based measures are described. A variety of hazards, mainly relating to inexperienced/untrained handlers, inappropriate handling, structural deficiencies of vehicles and facilities, poor driving conditions, unfavourable microclimatic and environmental conditions, and poor husbandry practices leading to these welfare consequences were identified. The Opinion contains general and specific conclusions relating to the different stages of transport for cattle. Recommendations to prevent hazards and to correct or mitigate welfare consequences have been developed. Recommendations were also developed to define quantitative thresholds for microclimatic conditions within the means of transport and spatial thresholds (minimum space allowance). The development of welfare consequences over time was assessed in relation to maximum journey duration. The Opinion covers specific animal transport scenarios identified by the European Commission relating to transport of unweaned calves, cull cows, the export of cattle by livestock vessels, the export of cattle by road, roll-on-roll-off ferries and 'special health status animals', and lists welfare concerns associated with these.

Effects of milk replacer allowances and levels of starch in pelleted starter on nutrient digestibility, whole gastrointestinal tract fermentation, and pH around weaning

The objectives of this study were to examine the effects of pelleted starter diets differing in starch and neutral detergent fiber (NDF) content when fed differing levels of milk replacer (MR) on nutrient digestibility, whole gastrointestinal tract fermentation, pH, and inflammatory markers in dairy calves around weaning. Calves were randomly assigned to 1 of 4 dietary treatments (n = 12 per treatment) in a 2 × 2 factorial design based on daily MR allowance and amount of starch in pelleted starter (SPS): 0.691 kg of MR per day [dry matter (DM) basis] with starter containing low or high starch (12.0% and 35.6% starch on DM basis, respectively), and 1.382 kg of MR per day (DM) with starter containing low or high starch. All calves were housed in individual pens with straw bedding until wk 5 when bedding was covered. Calves were fed MR twice daily (0700 and 1700 h) containing 24.5% crude protein (DM) and 19.8% fat (DM), and had access to pelleted starter (increased by 50 g/d if there were no refusals before weaning and then 200 g/d during and after weaning) and water starting on d 1. Calves arrived between 1 and 3 d of age and were enrolled into an 8-wk study, with calves undergoing step-down weaning during wk 7. Starting on d 35, an indwelling pH logger was inserted orally to monitor rumen pH until calves were dissected at the end of the study in wk 8. Higher SPS calves showed an increase in rumen pH magnitude (1.46 ± 0.07) compared with low SPS calves (1.16 ± 0.07), a decrease in rumen pH in wk 8 (high SPS: 5.37 ± 0.12; low SPS: 5.57 ± 0.12), and a decrease in haptoglobin in wk 8 (high SPS: 0.24 ± 0.06 g/L; low SPS: 0.49 ± 0.06 g/L). The majority of differences came from increased starter intake in general, which suggests that with completely pelleted starters the differences in starch and NDF do not elicit drastic changes in fermentation, subsequent end products, and any resulting inflammation in calves around weaning.

Impact of dietary supplementation of β-hydroxybutyric acid on performance, nutrient digestibility, organ development and serum stress indicators in early-weaned goat kids

The objective of this study was to determine the effect of dietary supplementation of β-hydroxybutyric acid (BHBA) on performance, nutrient digestibility, organ development, and serum composition in early-weaned goat kids. Sixty-four goat kids at 30 d of age were assigned to 4 treatments in a completely randomized design: 1) control (basal diet); 2) low (basal diet with 3 g/d per animal BHBA); 3) medium (basal diet with 6 g/d per animal BHBA; and 4) high (basal diet with 9 g/d per animal BHBA). Subsequently, 48 (6 kids per treatment) goat kids were randomly selected and slaughtered at 60 and 90 d of age. Compared with the control group, BHBA at low and high doses increased body weight (P < 0.05), average daily gain (P < 0.01), and average daily starter intake (P < 0.01). The BHBA improved organ development, especially at the lowest dose (P < 0.01). The digestibility of dry matter and crude protein increased with age (P < 0.05). However, BHBA did not affect nutrient digestibility. Compared with the control group, serum ceruloplasmin increased (P < 0.05) with high BHBA level at 90 d of age. However, the serum creatinine (P < 0.05) increased over time but was not affected by BHBA. The serum total antioxidant capacity and superoxide dismutase decreased with the high dose of BHBA at 90 d of age (P < 0.01). In contrast, the serum glutathione peroxidase and malondialdehyde increased with the high doses of BHBA (P < 0.01). Overall, low doses of BHBA were positive for growth performance, organ development, and health status against weaning stress. Whereas high doses of BHBA in the long term could negatively affect antioxidant status.

An Overview of Waste Milk Feeding Effect on Growth Performance, Metabolism, Antioxidant Status and Immunity of Dairy Calves

Waste milk (WM) is a part of the milk produced on dairy farms, which is usually unsuitable for human consumption. The WM contains transition milk, mastitis milk, colostrum, milk with somatic cells, blood (Hemolactia), harmful pathogens, pathogenic and antibiotic residues. Due to the high cost of milk replacer (MR), dairy farmers prefer raw WM to feed their calves. It has been well established that WM has a greater nutritive value than MR. Hence WM can contribute to improved growth, rumen development, and immune-associated parameters when fed to dairy calves. However, feeding raw WM before weaning has continuously raised some critical concerns. The pathogenic load and antibiotic residues in raw WM may increase the risk of diseases and antibacterial resistance in calves. Thus, pasteurization has been recommended as an effective method to decrease the risk of diseases in calves by killing/inhibiting the pathogenic microorganisms in the raw WM. Altogether, the current review provides a brief overview of the interplay between the positive role of raw WM in the overall performance of dairy calves, limitations of raw WM as a feed source and how to overcome these issues arising from feeding raw WM.

The impact of milk suckling protocol and schedule on body weight and some morphometric measurements of Holstein heifers

Having a successful heifer raising operation is not only relevant financially, but also influential for the future of the dairy herds. Milk feeding has a significant role on the health and growth of calves before weaning, in addition to the direct progressive effects on future performance post-weaning. Therefore, the aim of this study was to compare the effects of constants amount of milk (CMS) versus step-up/step-down (SUSD) on calf performance in two different suckling schedules of suckling milk gradually till 9th weeks of calf age, then decreasing it till weaning. For this study, forty Holstein heifers calves utilized between birth and 8 months of age were randomly divided into four groups of 10 calves each. Grouping was performed according to suckling protocol (constant versus variable) and suckling schedule (2 versus 3 times/day). Each calf suckled 600 kg of milk in a suckling period of 120 days. Body weight (BW), in addition to five body measurements: chest girth (CG), height at wither (HW), height at rump (HR), body length (BL), and diagonal length (DL), were recorded weekly. The heaviest BW was observed on SUSD calves suckling twice/day which had also the highest HW at weaning. Similarly, were BW, HW, and CG at 6 months of age. Also, the same group achieved the largest daily BW (0.902 kg/day), BL (0.246 cm), and CG (0.338 cm/day) gains during the pre-weaning phase. However, CMS suckled 3 times/day calves had the largest daily BW gain between birth and 6 or 8 months of age. CMS twice/day calves had the largest daily gain in CG from weaning to 6 months and from weaning to 8 months of age followed by SUSD suckling 3 times/day calves. Also, CMS twice/day calves had the largest daily gain in rump height from birth to 8 months of age compared to other groups. It can be concluded that when equal amounts of milk were fed during the suckling period, suckling protocol affected growth rate before weaning but that effect diminished as calf age increased after weaning.

Performance, structural growth, and digestibility by Holstein calves fed different amounts of milk through step-up/step-down or conventional methods

Early life milk intake can influence the survival and future productivity of replacement heifers. The present study determined the effects of different amounts of milk through step-up/step-down or conventional feeding methods on the performance of dairy calves. Thirty-nine Holstein calves (18 male and 21 female) were used in a completely randomized design. Calves were randomly allocated to 1 of 3 treatments: (1) conventional milk feeding (CONV; 4.5 L/d of milk from d 1 to 50 and 2 L/d of milk at d 51 and 52 of the study; total milk intake = 229 L); (2) low milk intake with step-up/step-down method (L-SUSD, 4 L/d of milk from d 1 to 10, 6 L/d from d 11 to 20, 8 L/d from d 21 to 30, 6 L/d from d 31 to 40, 4 L/d from d 41 to 50, and 2 L/d milk at d 51 and 52 of the study, total milk intake = 284 L); (3) high milk intake with step-up/step-down method (H-SUSD, 6 L/d of milk from d 1 to 10, 8 L/d from d 11 to 20, 10 L/d from d 21 to 30, 8 L/d from d 31 to 40, 6 L/d from d 41 to 50, 4 L/d milk at d 51, and 2 L/d milk at d 52 of the study, total milk intake = 386 L). All calves were weaned at d 52 and followed until d 70. Performance data (every week), skeletal growth (d 52 and 70), and ruminal fermentation parameters and digestibility (d 35, 55, and 70) were analyzed as repeated measurements with PROC MIXED of SAS version 9.3 (SAS Institute Inc.). A treatment × time interaction was observed for total dry matter intake (TDMI) as follows: TDMI differed among all treatments where H-SUSD > L-SUSD > CONV from d 11 to 38 of study, greater for H-SUSD versus other treatments from d 3 to 10 and d 39 to 70 of study. Starter feed intake and average daily gain (ADG) were greater in H-SUSD calves than in CONV calves, and L-SUSD treatment was intermediate for those traits. The H-SUSD calves tended to have greater body weight (BW) and lower feed efficiency than calves fed CONV or L-SUSD treatments. The treatments did not affect structural growth parameters, except for hip width, which tended to be greater in H-SUSD calves than CONV calves. Regardless of treatments, ADG, starter feed intake, BW, and body measurements increased as calves aged, whereas feed efficiency increased from d 1 to 52 of study and decreased from d 52 to 70 of study. The treatments had no effect on digestibility, rumen parameters, or fecal score. Overall, in calves that were weaned at 52 d and fed milk 3 times daily, the high milk intake (386 L) through the SUSD method did not increase diarrhea or decrease digestibility but increased starter feed intake and ADG.

Modeling Preweaning Dairy Calf Performance

The development of modeling concepts with the 2001 NRC (National Research Council Nutrient Requirements of Dairy Cattle represented a big step toward understanding and applying the underlying mechanisms associated with young calf growth. Factors such as the plane of nutrition being provided (protein and energy), breed and environmental stressors impact calf growth. Investigation into delivering the proper amounts of energy and protein through the liquid and dry feeds to optimize growth needs to continue as well as further defining the most effective means to transition from the nonruminant to ruminant phase while minimizing postweaning lag.

Effects of Milk Feeding Strategy and Acidification on Growth Performance, Metabolic Traits, Oxidative Stress, and Health of Holstein Calves

Effects of milk feeding strategy and acidification on calf growth, metabolic traits, oxidative stress, and health were evaluated in the first 78 days of life. Holstein calves (N = 48; 12 calves/treatment) were assigned to 1 of the 4 treatments in a 2 × 2 factorial arrangement of milk feeding strategy [6 L/d (MOD) or 12 L/d (HIGH) of milk] and acidification [non-acidified milk (NAM) or acidified milk (ACM)] on day 2. Calves were bucket-fed milk as follows: 6 L/d from days 2 to 49 for MOD and 6 L/d from days 2 to 49, 12 L/d from days 7 to 42, and 8 L/d from days 43 to 49 for HIGH calves. All calves were then fed 4 L/d from days 50 to 56. Starter and water were available ad libitum, while hay was fed at 5% of starter from day 64. Calves were weighed, measured, and blood (except days 14, 42 and 56) sampled on days 2, 14, 28, 42, 49, 56, 63 and 78. Data were analyzed using Mixed PROC of SAS with time as repeated measurements. Fecal scores, checked daily, were examined by the logistic regression using a binomial distribution in GLIMMIX procedure. There were no three-way interactions observed for all the parameters. We detected a milk feeding strategy × time interaction for starter intake, body weight, ADG, ADG/ME, FE, structural measurements, and glucose. Although, overall (558.0 vs. 638.6 g/d), HIGH calves tended to consume less starter compared to MOD, significant differences were only observed in week 8. The HIGH calves had greater ADG during days 2–14 (1.12 vs. 0.75 kg/d) and tended to have greater ADG on days 15–28 (0.79 vs. 0.55) and 29–42 (0.86 vs. 0.60) and lower on days 57–63 (0.11 vs. 0.38) compared to MOD calves. The HIGH calves had greater BW from days 28 to 78 compared to MOD, while NAM were bigger compared to ACM calves from days 49 to 78. The HIGH calves had lower overall feed and metabolizable energy efficiencies compared to MOD. Except for BW and heart girth, no milk acidification × time interaction was observed for starter intake, ADG, FE, or ADG/ME. Blood glucose in calves fed NAM-HIGH and ACM-HIGH were greater compared to those fed moderate milk volumes on day 28 only. Albeit, feeding strategy had no effect, calves fed ACM had lower likelihood of experiencing diarrhea (odds ratio = 1.32; 95% confidence interval: 1.018–1.698) compared to those fed NAM. Overall milk feeding strategy had no effect on growth, while milk acidification reduced growth in calves, despite lowering the likelihood of experiencing diarrhea.

Effects of Age and Dietary Factors on the Blood Beta-Hydroxybutyric Acid, Metabolites, Immunoglobulins, and Hormones of Goats

The study was aimed to examine the effects of age and dietary beta-hydroxybutyric acid (BHBA) on blood BHBA and blood health indicators in goat kids. Thirty male goats of five ages (1, 2, 3, 6, and 12 months old) were selected for blood sampling to determine the influence of age. Another 64 goat kids (half males and half females) were weaned at 1 month old and fed with starter diets with control, low, medium, and high BHBA doses (0, 3, 6, and 9 g/animal/day, respectively). Six goats per treatment were selected for blood analysis at 2 and 3 months of age. There were significant effects (p < 0.01) of ages on the blood parameters of goat kids. The 6- and 12-month-old goats showed significantly lower blood total protein, globulin, BHBA, IgA, and IgM concentrations than did young goats, while they had a higher albumin-to-globulin ratio than young goats. The blood glucose decreased (p < 0.01) and IgG increased over time (p < 0.01). In blood, growth hormone (GH) and insulin-like growth factor I (IGF-I) were lower (p < 0.01) at 1- and 3-month-old goats than 12-month-old goats. The high dietary BHBA improved (p < 0.05) the ratio of albumin to globulin of 2-month-old kids compared with control. The blood GH and IGF-I were lower (p < 0.01) in the medium BHBA dose at 2 months of age than control. These results suggested that age greatly impacted blood composition, especially around weaning, and dietary BHBA showed beneficial regulating effects on blood total protein level in young goats.

Milk feeding level and starter protein content: Effects on growth performance, blood metabolites, and urinary purine derivatives of Holstein dairy calves

The objective of this study was to investigate the effects of milk allowances equal to 526 g/d as moderate (MOD) versus 790 g/d of milk dry matter as high (HI), and starter diets containing 18% or 23% crude protein (CP), on growth performance, blood metabolites, and purine derivative (PD) excretion in the urine of dairy calves. A total of 52 female Holstein dairy calves (40.8 kg of body weight) were randomly assigned to the experimental diets. The treatments were (1) moderate milk and 18% CP starter diet (MOD-18CP); (2) MOD and 23% CP starter diet (MOD-23CP); (3) high milk and 18% CP starter diet (HI-18CP); and (4) HI and 23% CP starter diet (HI-23CP). Calves had free access to a starter feed and water and were weaned on d 53 but remained in the study until d 73. Urine samples were collected during the preweaning period (for 6 consecutive days between d 35 and 40) and postweaning period (for 6 consecutive days between d 65 and 70) to investigate urinary excretion of PD. Starter feed intake, β-hydroxybutyrate (BHB), and blood urea concentrations were reduced; however, average daily gain (ADG) and blood glucose levels increased in calves fed HI before weaning compared with MOD. During the preweaning period, high milk feeding increased total urinary PD excretion but decreased it after weaning. The 23CP diet resulted in higher feed intake and ADG before weaning and higher excretion of allantoin and total excretion of PD compared with the 18CP diet. The HI-23CP treatment resulted in the greatest withers and hip heights at weaning and final measurement, as well as the highest preweaning blood insulin concentrations. In terms of rumen development, MOD-23CP showed the greatest benefits based on starter intake, blood BHB concentration, and urinary excretion of PD. Based on the higher urinary excretion of PD found in HI-fed calves before weaning, it is possible that milk feeding overestimates estimated microbial yield. The results suggest that feeding starters with a higher proportion of CP may help maintain a more balanced ratio of CP to ME during high milk feeding, to avoid protein deficiency due to low starter intake. When calves are fed a high milk allowance, urine excretion of PD may be misinterpreted as a measure of estimated microbial growth and rumen development; this should be considered during calculations of estimated microbial yield in milk-fed calves.

Feeding rumen-protected lysine to dairy cows prepartum improves performance and health of their calves

Providing adequate concentrations of AA in the prepartum diet is pivotal for the cow's health and performance. However, less is known about the potential in utero effects of particular AA on early-life performance of calves. This experiment was conducted to determine the effects on dairy calves when their dams were fed rumen-protected lysine (RPL; AjiPro-L Generation 3, Ajinomoto Heartland Inc.; 0.54% dry matter of total mixed ration as top dress) from 26 ± 4.6 d (mean ± standard deviation) before calving until calving. Seventy-eight male (M) and female (F) Holstein calves were assigned to 2 treatments based on their dams' prepartum treatment, RPL supplementation (PRE-L) or without RPL (CON). At the time of birth (0.5-2 h after calving), before colostrum was fed, blood samples were collected. An initial body weight was obtained at 1 to 3 h after birth. Calves were fed 470 g of colostrum replacer (Land O'Lakes Bovine IgG Colostrum Replacer, Land O'Lakes, Inc.) diluted in 3.8 L of water. Calves were provided water ad libitum and fed milk replacer (Advance Excelerate, Milk Specialties Global Animal Nutrition; 28.5% crude protein, 15% fat) at 0600 h and 1700 h until 42 d of age. Calves were measured weekly, at weaning (d 42), and at the end of the experimental period (d 56). Plasma concentrations of AA were measured on d 0, 7, and 14 d using ultra-performance liquid chromatography-mass spectrometry (Waters) with a derivatization method (AccQ-Tag Derivatization). Final body weight was greater for M (87 ± 11 kg) than F (79 ± 7 kg). Calves in PRE-L tended to have greater dry matter (814 ± 3 g/d) and crude protein (234 ± 6 g/d) intakes than those in CON (793 ± 9 g/d and 228 ± 11 g/d, respectively). Calves in PRE-L had greater average daily gain (0.96 ± 0.04 kg/d) than calves in CON (0.85 ± 0.03 kg/d) during wk 6 to 8. Calves in PRE-L tended to be medicated fewer days than CON (4.7 ± 1.2 d vs. 6.2 ± 3.4 d, respectively). Calves in PRE-L-M and CON-F (2,916 ± 112 µM and 2,848 ± 112 µM, respectively) had greater total AA concentration in plasma than calves in PRE-L-F and CON-M (2,684 ± 112 µM and 2,582 ± 112 µM, respectively). Calves in PRE-L-F and CON-M (4.09 ± 0.11% and 4.16 ± 0.11%, respectively) had greater concentration of Lys as a percentage of total AA compared with calves in CON-F and PRE-L-M (3.91 ± 0.11% and 3.90 ± 0.11%, respectively). Calves in PRE-L tended to have greater percentage of phagocytic neutrophils (39.6 ± 1.59%) than calves in CON (35.9 ± 1.59%). In conclusion, increasing the metabolizable lysine provided to prepartum dairy cows had modest effect over offspring performance, with the major result being a greater average daily gain for calves in PRE-L during the preweaning phase (wk 6-8).