Invited review: The importance of colostrum in the newborn dairy calf

It is critical that bovine maternal colostrum is fed to newborn calves during their first hours of life. Colostrum is the secretion a cow produces after mammary involution that is rich in various nutrients. In addition to the nutritive value for newborn calves, immunoglobulins are of interest due to their role in developing the naïve immune system of calves at birth. The process by which a calf acquires immunity via absorption of immunoglobulins is defined as passive immunity. When calves consume an adequate amount of immunoglobulins, they are classified as having successful passive immunity (SPI). In contrast, if they are deprived of adequate colostrum, they are considered to have had a failure of transfer of passive immunity (FPI). Transfer of passive immunity is assessed by measuring serum IgG concentrations at 24 to 48 h of age. The major factors that influence whether a calf has SPI or FPI are colostrum IgG concentration, quantity fed, and age of calf at colostrum feeding. Monitoring apparent efficiency of immunoglobulin absorption in calves is often recommended to evaluate overall colostrum management practices. Serum IgG analyses can be determined with direct (radial immunodiffusion) or indirect (refractometry) methods and used to assess SPI or FPI prevalence.

Starch-protein interaction in the rumen of weaned dairy calves

The objectives of this study were to investigate the effect of starch and protein interaction on rumen environment, in situ digestion, and total-tract digestibility of nutrients in weaned dairy calves between 8 and 16 wk of age. Sixteen rumen-cannulated calves were randomly divided into 4 dietary treatment groups with 4 calves fed in each treatment. The treatment diets had 2 levels of starch [18%, low starch (LS), or 38%, high starch (HS)] and 2 levels of protein [16%, low protein (LP), or 22%, high protein (HP)] on a dry matter (DM) basis in calf grower: (1) LPLS, (2) LPHS, (3) HPLS, and (4) HPHS. Calves were fed for ad libitum intake (95% assigned grower and 5% grass hay), and refusals were collected weekly. Total-tract digestibility collection and in situ digestibility procedures were performed for each calf at 11 and 15 wk. Samples for in situ digestibility, grass hay (GH), soybean hulls (SBH), wheat middlings (WM), ground corn (GrC), and soybean meal (SBM) were incubated for 9 and 24 h. There was no starch and protein interaction on total-tract digestibility of calves. Total-tract DM, neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility, and feed efficiency were affected by both protein and starch inclusion level in calf diet. Total-tract starch digestibility was lower for LS diets. Dry matter digestibility and feed efficiency were greater in calves fed HP and HS diets compared with calves fed LP and LS diets, respectively. Fiber digestibility (NDF and ADF) was less in calves fed HS diets compared with calves fed LS diets but was greater in calves fed HP diets compared with calves fed LP diets. Level of protein did not affect in situ DM and NDF disappearance of GH, but HP increased in situ DM and NDF disappearance of SBH. High-starch diets decreased DM and NDF disappearance of both GH and SBH. At 20 h after feeding, ruminal pH was 0.51 unit higher in calves fed HPHS compared with calves fed LPHS. Total ruminal VFA and proportion of propionate was greater with HS versus LS, whereas proportion of acetate was greater with LS versus HS. The DM disappearance of SBM and WM and NDF disappearance of WM was greater for calves fed HPHS compared with calves fed LPHS at 11 wk of age. In our study, when HP was fed with HS, rumen pH, in situ digestion of WM and SBM, and total-tract digestion of DM, NDF, and ADF increased. This provides evidence for starch-protein interaction in the rumen of recently weaned dairy calves. Improvements in total-tract and in situ digestibility suggest that both protein and starch levels are important for 8- to 16-wk-old calves.

Replacing soybean hulls with grass hay on growth, intake, total tract digestibility, and rumen microbial nitrogen production of weaned Holstein dairy calves from 8 to 16 weeks of age

The objective of this experiment was to determine the effects of replacing soybean hull (SBH) pellets with grass hay (GH) on growth, intake, total-tract digestibility, and rumen microbial nitrogen production of weaned dairy calves from 8 to 16 wk of age. Holstein calves (n = 16) were randomly assigned to 1 of 4 rations containing, on a dry matter (DM) basis, 76% grower with the remaining 24% being made up of different amounts of SBH pellets and GH [0% GH, 24% SBH (0GH); 8% GH, 16% SBH (8GH); 16% GH, 8% SBH (16GH); and 24% GH, 0% SBH (24GH)]. Calves were weaned at 6 wk, housed individually, and studied from 8 to 16 wk of age. From 8 to 9 wk of age calves were offered a ration consisting of 50% of texturized starter (20% CP and 35% starch), which was offered from 3 d of age, and 50% of their assigned ration. From 9 wk until the end of the study, calves were offered 100% of their assigned ration. Intake and body weight were measured weekly, and frame measurements were taken at the beginning and end of the study. Animal behavior observations were recorded every 5 min over a 24-h period at 10 and 14 wk of age. Total fecal and urine collection was conducted for 4 d consecutively at 11 and 15 wk of age. Feed and feces were evaluated for DM, N, neutral detergent fiber, acid detergent fiber, and starch to determine total-tract digestibility. Feces were evaluated for geometric mean particle length (Xgm) and particle size distribution. Urine was evaluated for N, creatinine, urea, and total purine derivatives to estimate microbial N yield. Calves offered 0GH and 8GH had a 20% increase in intake, average daily gain (1.23, 1.27, 0.89, and 0.71 kg/d for 0GH, 8GH, 16GH, and 24GH, respectively), and feed efficiency compared with 16GH and 24GH. Calves offered 8GH had the greatest levels of neutral detergent fiber and acid detergent fiber digestibility, as well as the greatest estimated microbial N yields. Inclusion of forage increased rumination time (2.75, 6.89, 7.18, and 8.16 h/d for 0GH, 8GH, 16GH, and 24GH, respectively) and decreased fecal Xgm by ~35% compared with calves offered 0GH. In the current study, increasing the replacement of SBH with GH beyond 8% was detrimental to weaned calf performance. These results indicate that when diets containing 8% GH and 16% SBH were fed to recently weaned calves, rumen functionality and feed efficiency were optimized compared with the other GH-SBH combinations.

Relationship of body weight at first calving with milk yield and herd life

The objectives of this study were to investigate the association of body weight (BW) at first calving (BWFC) and maturity rate (MR; BWFC as a percentage of mature BW) with first-lactation 305-d milk yield (FLMY), milk yield (MY) in the 24 mo following first calving (24MMY), herd life, and BW change (BWC) through the first month of lactation in Holstein heifers. We retrieved daily milk production records and daily BW records from AfiFarm (S. A. E. Afikim, Kibbutz Afikim, Israel). The data set included daily records for 1,110 Holstein cows from The Pennsylvania State University (n = 435,002 records) and 1,229 Holstein cows from University of Florida (n = 462,013 records) that calved from 2001 to 2016. Body weight at first calving was defined as mean BW from 5 to 10 d in milk of the first lactation, whereas BWC represented change from BWFC to average BW from 30 to 40 d in milk. First-lactation 305-d MY and 24MMY were analyzed with a linear model that included effects of farm-year-season of calving, age at calving, and quintiles of BWFC, MR, or BWC. Body weight change was analyzed with the same model to determine associations with BWFC. Survival analysis was performed to estimate the effect of BWFC on survival. Heifers in the top 60% of BWFC had significantly higher FLMY (10,041 to 10,084 kg) than lighter heifers (9,683 to 9,917 kg), but there was wide variation in every quintile, and no relationship of BWFC and FLMY existed within the top 60%. Relationships between BWFC and 24MMY were not significant. Heifers with higher BWFC or MR lost significantly more BW in early lactation. Although BWFC and MR were significant predictors of FLMY, they accounted for <3% of variation in FLMY or 24MMY, suggesting that BWFC and MR are not primary contributors to variation in MY. Compared with the lightest heifers, the heaviest heifers were 49% more likely to be culled at a given time. These data indicated that, among heifers managed similarly, heavier heifers produced more milk in first lactation than lighter heifers but lost more BW, faced a higher risk of being culled, and did not produce more milk in the long term. Based on our data, heifers that reach between 73 and 77% MR at first calving can produce more milk in their first lactation without sacrificing long-term MY and herd life.

Increasing grass hay inclusion level on weaned dairy calf growth, intake, digestibility, and ruminal fermentation

The objective was to determine effects of increasing grass hay (GH) inclusion level on weaned dairy calf growth, intake, digestibility, and ruminal fermentation. Holstein calves (n = 45) were randomly assigned to 1 of 3 total mixed rations with increasing GH [10, 17.5, or 25% on a dry matter (DM) basis; LGH, MGH, or HGH, respectively]. Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of texturized calf starter (20% crude protein) and coarsely chopped GH, were offered ad libitum as separate components from 7 to 9 wk of age. After 9 wk, feed was offered as a total mixed ration containing the assigned level of GH and fed according to the clean bunk feeding strategy as a means of limiting refusals. Initial 9-wk body weight was 81.6 ± 9 kg (mean ± standard deviation). Intake and growth were measured weekly. Blood samples were collected at 9, 10, 12, 14, and 16 wk of age for analysis of plasma glucose and β-hydroxybutyrate. Total fecal collection (12 calves; 4 per treatment) was conducted at 11 and 15 wk of age for 4 d consecutively. Rumen samples were collected over the final 24 h of each fecal collection period to evaluate pH and volatile fatty acid profile. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to estimate total-tract digestibility. Intake and weight gain were analyzed from 7 to 9 wk and 9 to 16 wk, representing pretreatment and treatment periods. No differences were observed between treatments from 7 to 9 wk. However, differences were found from 9 to 16 wk. Final body weight, average daily gain, DM intake, and metabolizable energy intake all decreased with increased GH. However, skeletal frame measurements did not vary between treatments. Plasma β-hydroxybutyrate tended to decrease with increased GH. No differences were observed in DM or starch digestibility, but neutral detergent fiber and acid detergent fiber digestibility increased with increased GH. Mean rumen pH and total volatile fatty acid did not change with increasing GH inclusion; however, there was an interaction with time indicating that ruminal fermentation patterns throughout the day were different for calves offered MGH and HGH versus those offered LGH. These results indicate that feeding levels of GH >10% reduce growth and intake before 16 wk and alter ruminal fermentation patterns.

Feeding various forages and live yeast culture on weaned dairy calf intake, growth, nutrient digestibility, and ruminal fermentation

The objective of this study was to determine effects of various forages and live yeast culture on intake, growth, nutrient digestibility, and ruminal fermentation of weaned dairy calves. Holstein calves (n = 45) were randomly assigned to 2 × 3 factorial treatments: live yeast culture or no yeast and alfalfa haylage (AH), corn silage (CS), or grass hay (GH). Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 16 wk of age. Rations, consisting of an 18% crude protein texturized grower (yeast or no yeast) and assigned forage, were offered as separate components until 9 wk of age. After 9 wk, diets were offered as a total mixed ration (TMR). Concentrate intake was capped at 2.25 kg of dry matter (DM)/d, and forage was offered ad libitum. The TMR contained equal forage neutral detergent fiber (8 ± 0.5%) on a DM basis for each basal diet. Calves were fed TMR to limit concentrate intake, and additional forage was offered ad libitum after 8 h if the entire TMR allotment was consumed. Total fecal collection (12 calves) was conducted for 4 d at 11 and 15 wk of age. Feeds and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and starch to calculate digestibility. On the last day of fecal collection, rumen samples were collected to evaluate pH and volatile fatty acid (VFA) profile. Metabolizable energy and DM intake was least for calves consuming GH compared with other forages. Forage intake (% of DM intake) increased as calves aged (AH = 20 to 44.4%, CS = 24.5 to 37.6%, GH = 11.3 to 32.3% at 10 and 16 wk of age, respectively). Calves on CS had the greatest average daily gain and empty body weight gain, and calves on GH had the least. Calves on GH tended to have the lowest final body weight. There were no differences in structural growth. Digestibility of DM decreased with age. Fiber digestibility was least for calves on CS, and starch digestibility was least for calves on AH. Mean and minimum rumen pH increased with age. Forage offered changed VFA profile and there was an interaction between yeast and forage on VFA profile. These results indicated that recently weaned calves perform well on AH, CS, or GH and have minimal benefit from yeast supplementation. Feeding GH reduced weight gain, but all calves achieved a level of gain to meet growth goals for breeding and freshening. Furthermore, the ability to consume large portions of the ration as forage allows for more economical diets to be fed.

Short communication: Variation in serum immunoglobulin G concentrations from birth to 112 days of age in Holstein calves fed a commercial colostrum replacer or maternal colostrum

Serum IgG concentrations in dairy calves change throughout their first weeks of life, peaking at 24 h and then steadily decreasing until calves begin to produce endogenous IgG. The objective of this study was to observe serum IgG dynamics from birth until 16 wk of life in calves fed either maternal colostrum (MC) or colostrum replacer (CR). A total of 44 Holstein calves were randomly assigned to 1 of the 4 colostrum treatments and followed throughout the study. Treatments consisted of feeding high-quality MC, low-quality MC supplemented with CR, or 1 of 2 distinct levels of IgG concentration from CR. Overall, the interaction between type of colostrum fed and sampling time was significant. Individual differences for this effect were found at d 1, 7, 14, 21, 28, and 98, while the other time points were not different.

Consensus recommendations on calf- and herd-level passive immunity in dairy calves in the United States

Passive immunity in calves is evaluated or quantified by measuring serum or plasma IgG or serum total protein within the first 7 d of age. While these measurements inform about circulating concentrations of this important protein, they are also a proxy for evaluating all of the additional benefits of colostral ingestion. The current individual calf standard for categorizing dairy calves with successful passive transfer or failure of passive transfer of immunity are based on serum IgG concentrations of ≥10 and <10 g/L, respectively. This cutoff was based on higher mortality rates in calves with serum IgG <10 g/L. Mortality rates have decreased since 1991, but the percentage of calves with morbidity events has not changed over the same time period. Almost 90% of calves sampled in the USDA National Animal Health Monitoring System's Dairy 2014 study had successful passive immunity based on the dichotomous standard. Based on these observations, a group of calf experts were assembled to evaluate current data and determine if changes to the passive immunity standards were necessary to reduce morbidity and possibly mortality. In addition to the USDA National Animal Health Monitoring System's Dairy 2014 study, other peer-reviewed publications and personal experience were used to identify and evaluate potential standards. Four options were evaluated based on the observed statistical differences between categories. The proposed standard includes 4 serum IgG categories: excellent, good, fair, and poor with serum IgG levels of ≥25.0, 18.0-24.9, 10.0-17.9, and <10 g/L, respectively. At the herd level, we propose an achievable standard of >40, 30, 20, and <10% of calves in the excellent, good, fair, and poor categories, respectively. Because serum IgG concentrations are not practical for on-farm implementation, we provide corresponding serum total protein and %Brix values for use on farm. With one-third of heifer calves in 2014 already meeting the goal of ≥25 g/L serum IgG at 24 h of life, this achievable standard will require more refinement of colostrum management programs on many dairy farms. Implementation of the proposed standard should further reduce the risk of both mortality and morbidity in preweaned dairy calves, improving overall calf health and welfare.

Effect of converting weaned dairy calves from a component-fed diet to a total mixed ration on growth and nutrient digestibility

The objective was to determine the effects of converting calves from a component-fed ration to a total mixed ration (TMR) at 8, 10, or 12 wk of age on intake, growth, and nutrient digestibility. Holstein calves (n = 40) were randomly assigned to 1 of 4 groups (no TMR, TMR conversion at 8, 10 or 12 wk; T0, T8, T10, and T12, respectively). Calves were weaned at 6 wk of age, housed individually, and studied from 7 to 14 wk of age. Rations, consisting of a 20% crude protein texturized starter and grass hay, were offered ad libitum as separate components or as a TMR with 85% starter and 15% grass hay on a dry matter (DM) basis. Intakes and body weights (BW) were measured weekly. Component intake for TMR was calculated from the proportion of grass hay and starter contained in the TMR. Fecal grab samples were collected every 9 h over 3 d for a total of 8 samples that formed a composite at 9, 11, and 13 wk of age from the same 4 calves per group. Rumen fluid samples were collected via esophageal tube at -1, 0, 3, and 7 d relative to conversion from component to TMR. Feed and feces were evaluated for DM, neutral detergent fiber, acid detergent fiber, and acid detergent lignin (internal flow marker) to estimate digestibility. Average daily gain and final BW tended to be least for T8. Empty BW gain was significantly less for T8 than for T0 but not different from T10 or T12 (T0 = 1.07, T8 = 0.93, T10 = 1.02, T12 = 1.04 kg/d). Hip growth tended to be least for T8 and resulted in lower final hip width (T0 = 25.9, T8 = 25.2, T10 = 25.6, T12 = 25.8 cm). Intake tended to be reduced for calves converted to TMR earlier. Throughout the study, calves fed TMR ate more hay and less starter than component-fed calves. Metabolizable energy intake was less for T8 versus T0 but not different from T10 or T12 (T0 = 8.46, T8 = 7.55, T10 = 8.01, T12 = 8.23 Mcal/d). We observed no differences in feed efficiency for the duration of the study. Differences in DM digestibility were not observed, but fiber digestibility was greater for calves fed TMR at 9, 11, and 13 wk of age. Conversion to TMR increased rumen pH. These results indicate that TMR conversion increased hay consumption and subsequently decreased starter and total DM intake. This led to reduced weight and structural growth; however, calves that were converted to TMR as early as 8 wk still achieved adequate growth. The increase in rumen pH and subsequent increase in fiber digestibility allowed for calves to be converted to a 15% grass hay TMR as early as 8 wk and still achieve desirable growth goals.

Comparison of immunoglobulin G absorption in calves fed maternal colostrum, a commercial whey-based colostrum replacer, or supplemented maternal colostrum

Successful passive transfer of antibodies in neonatal calves can be achieved by feeding an adequate quantity and quality of maternal colostrum (MC) or colostrum replacer (CR). An alternative could be feeding low-quality maternal colostrum (LMC) with added IgG from a CR. The objective of this study was to determine if a commercial whey-based CR product containing low levels of casein (Premolac PLUS Bovine IgG; Zinpro Corporation, Eden Prairie, MN) fed to replace MC or supplement LMC could lead to adequate serum IgG levels and apparent efficiency of absorption (AEA) in neonatal dairy calves. Holstein calves (n = 20 per treatment) were separated from their dam after birth and randomly assigned to be fed 3.79 L of MC (106 g/L of IgG; 401 g of IgG fed), LMC (30 g/L IgG) supplemented with CR (41 g/L IgG; 154 g of IgG total fed; LMC-CR), or 1.3 L of 1 of 2 levels of CR (110 or 150 g of IgG fed; CR-110 or CR-150) within 1.5 h of birth. Colostrum was obtained from the first (MC) or second and third milkings (LMC) of cows from Pennsylvania State University dairy and pooled by source into large batches. Blood samples were taken from calves before colostrum feeding and 24 h after birth and were analyzed for serum total protein, total IgG, hematocrit, and Brix percentage. Calves fed MC had higher 24-h IgG values (means ± SEM) than calves fed LMC-CR (27.04 ± 1.07 vs. 22.33 ± 1.08 mg/mL, respectively). Feeding 150 g of IgG from CR led to higher 24-h serum IgG values than feeding 110 g of IgG (16.90 ± 1.09 vs. 12.79 ± 1.08 mg/mL). Serum IgG levels were different between the CR-fed calves and the calves fed LMC-CR and MC, but all had average values >10 mg/mL IgG. Calves fed LMC-CR had greater AEA than calves fed MC (54.58 ± 2.39 vs. 24.38 ± 2.36%, respectively). Among calves fed CR-110 or CR-150, AEA did not differ. Serum total protein and Brix percentage had strong correlations with actual IgG values across the entire study. We found no differences in average daily gain or health variables measured, and no differences in final hip width, withers height, or body weight for calves fed MC, LMC-CR, CR-150, or CR-110. These results indicate that CR can be fed successfully as an alternative to MC or as a supplement to colostrum with low IgG.

Symposium review: Strategies to improve the efficiency and profitability of heifer raising

Regional Research Project NC-2042 has a main objective to study calf and heifer nutrition. Within this objective, feeding the postweaned heifer is considered a major priority to improve the profitability and sustainability of US dairy farms. Through optimizing nutrient utilization by precision feeding, using alternative feeds, high-fiber diets, and feed additives, this research group has worked to enhance dairy heifer nutrition. Research has focused on precision feeding heifers and incorporating high- and low-fiber diets into this system of feeding. This is accomplished by meeting the nutrient needs of the heifer for a desired rate of growth while enhancing total-tract nutrient digestibility, reducing waste and improving profitability. High-fiber forages have been studied as a means of controlling ad libitum dry matter intakes and thus weight gain in heifers. These results provide producers with a means of feeding heifers while reducing costs. Similarly, utilizing alternative feedstuffs in heifer diets has also been a major research area for this group including comprehensive research on distillers co-products, and new protein sources such as camelina and carinata meals. Results indicated that these products can be satisfactorily incorporated into heifer diets. Studying feed additives has also been a function of the research group. Research with Ascophyllum nodosum and cinnamaldehyde indicated that calves find these additives unpalatable and that supplementing cinnamaldehyde to postweaned heifers showed no benefit. However, sodium butyrate and yeast supplementation proved to be beneficial in the growth and feed efficiency of heifers. Research from this group has an effect on heifer feeding, resulting in new information that can aid in the sustainability of dairy farms. This review will focus on the area of postweaned heifer nutrition.

Symposium review: Colostrum management and calf nutrition for profitable and sustainable dairy farms

Multistate dairy management research project NC-2042, which is part of the National Institute of Food and Agriculture, has devoted an ongoing objective to calf and heifer nutrition and management. Within this objective, colostrum research has been a priority due to continued opportunities to improve this area on US dairy farms. Research has focused on heating colostrum to reduce bacterial populations and pathogens while increasing IgG absorption. Research also identified other proteins that are reduced when heating colostrum. Studies indicated an apparent upper limit to IgG absorption from colostrum fed to calves. Additional studies have shed light on absorption of IgG from colostrum replacers and evaluated the use of lactoferrin and sodium bicarbonate in both maternal colostrum and colostrum replacers. Milk replacer formulation, feeding strategies, and the effect of calfhood nutrition on future performance have also been researched. Finally, water quality and its effect on calves and heifers have been studied. This review focuses on research done by multistate research project NC-2042 member states in the area of colostrum and calf nutrition and management.

Short communication: Relationships between physical form of oats in starter, rumen pH, and volatile fatty acids on hepatic expression of genes involved in metabolism and inflammation in dairy calves

In early-weaning programs, dietary effects on calf rumen development have been studied extensively, but very little information is available about the effects of a solid diet on hepatic metabolism in preweaned dairy calves. The objective of this experiment was to determine the effect of physical form of oats in calf starter on the expression of key hepatic gluconeogenic, β-oxidation, and acute phase protein genes in preweaned dairy calves. Samples were analyzed from 3 experiments that fed either ground or whole oats in calf starters. Briefly, 7 calves were slaughtered at 5 wk of age in experiment 1, 6 were slaughtered at 6 wk in experiment 2, and 7 were slaughtered at 7 wk in experiment 3, and liver tissue was collected for gene expression analysis. Calves from experiments 1 and 2 were cannulated, and their rumen pH and volatile fatty acids were measured during treatment periods. The mRNA expression of gluconeogenic enzymes pyruvate carboxylase (PC), cytosolic and mitochondrial phosphoenolpyruvate carboxykinase (PCK1 and PCK2), fatty acid oxidation enzyme carnitine palmitoyltransferase I (CPT1), and positive acute phase protein haptoglobin (HPT) was measured by real-time quantitative reverse-transcriptase PCR. Expression of HPT was greater in calves fed whole oats than in calves fed ground oats; however, PC, PCK1, PCK2, and CPT1 were not affected by the physical form of oats. All enzymes (PCK1, PCK2, HPT, and CPT1) except PC were affected by experiment; PCK1 and CPT1 had greater expression in experiment 2 than in experiments 1 and 3. Expression of PCK2 was similar in experiments 2 and 3 but greater than experiment 1. Expression of HPT was similar in experiments 1 and 2 but greater than experiment 3. The mRNA expression of enzymes PCK1, PCK2, and CPT1 differed between experiments 1 and 2 and was negatively correlated with rumen propionate and butyrate but had a positive relationship with rumen acetate. Similarly, rumen pH was different in experiments 1 and 2, averaging 5.69 in experiment 1 and 4.81 in experiment 2, and there was a negative correlation between mRNA expression of rate-limiting gluconeogenic PCK1, PCK2, and β-oxidation CPT1 enzymes and rumen pH of calves in experiments 1 and 2. We concluded that the physical form of oats in calf starter did not affect gene expression of gluconeogenic and β-oxidation enzymes in preweaned dairy calves. However, lower rumen pH may be related to the upregulation of these enzymes.

Fecal particle dry matter and fiber distribution of heifers fed ad libitum and restricted with low and high forage quality

Wet sieving of manure can be used as a means of evaluating the nutrient utilization of diets by dairy cows. A commercially available system for this analysis (Nasco Digestion Analyzer, Nasco, Fort Atkinson, WI; NDA) employs principles of wet sieving for on-farm assessment. The objective of this study was to evaluate effects of diet manipulations and sampling techniques on fecal particle dry matter (DM), neutral detergent fiber (NDF), and starch distribution on NDA sieves. Eight Holstein heifers (means ± SD; age 18.4 ± 0.6 mo and BW 457.2 ± 27.3 kg), were randomly assigned to a split-plot 4 × 3 incomplete Latin square experimental design with 18-d periods (15 d of adaptation and 3 d of sampling). Treatment rations differed in forage quality (high ADF <35%, low ADF >35%) and fiber content (high NDF >45%, low NDF <40%) and were offered to heifers for ad libitum and restricted intakes. Diets were fed to allow 900 to 1,000 g/d of body weight gain and fed once daily. Fecal grab samples were collected 0, 6, 12, and 18 h after feeding all 3 d of the sampling period, and the remaining feces was collected in the manner of total fecal collection to represent a daily composite sample. After wet sieving of each sample using a NDA kit, the retained material on sieves was dried and analyzed for DM, NDF, and starch content. Sampling day and feeding regimen did not affect distributions of nutrients. Distributions of total fecal particle DM were greater for high forage quality and high fiber content diets (14.66 to 20.37% of sample DM). The NDF content in retained material decreased with decreasing sieve size (from 89.81 to 86.86%) and was not affected by forage quality and fiber content, whereas NDF retained on NDA (% DM) followed the same pattern as the retained particle DM weight. Starch content in retained material was below 0.5% in the majority of diets. Average retained fecal particle DM and NDF content varied depending on the time after feeding, resulting in the large differences between grab fecal samples and a daily total composite sample. However, average values of retained particle DM and NDF weight for all sampling time points were similar to ones from total daily composite sample.

Effects of once- versus twice-a-day feeding of pasteurized milk supplemented with yeast-derived feed additives on growth and health in female dairy calves

The objective of this study was to compare the effects of feeding preweaning dairy calves pasteurized milk once or twice a day with or without a combination of yeast-derived products. Holstein heifer calves (n = 48) from The Pennsylvania State University dairy herd were fed 3.8 L of colostrum in 1 feeding and randomly assigned to 1 of 4 treatments (once-a-day milk feeding with or without live yeast culture and mannan-rich fraction and twice-a-day milk feeding with or without live yeast culture and mannan-rich fraction). All calves were fed 6 L of milk daily. Weekly growth measurements and blood samples were taken 3 h after the morning milk feeding for all animals. Growth measurement included body weight, hip width, and withers height. Calf starter refusal was recorded weekly, and a sample was taken to determine dry matter intake. Daily health scores were recorded for each calf using a standard scoring system. Intake, growth measurements, haptoglobin, and health scores data were analyzed using repeated measures analysis with calf included as a random variable. Preweaning average daily gain was 553.4 and 512.1 g/d for calves fed milk once and twice a day, respectively, and we found no difference between treatments. Preweaning calf starter intake was 242.3 and 198.7 g/d for calves fed milk once and twice a day, respectively, and we found no treatment differences. Preweaning calf starter intake was 224.3 and 216.6 g/d for calves fed yeast and without yeast, respectively. Withers height and hip width were similar in calves fed milk either once or twice a day; however, calves fed yeast tended to have greater withers height and hip width than control calves. Haptoglobin concentration as a measure of stress had least squares means of 4.0 and 9.5 ± 3.5 µg/mL for calves fed milk once or twice a day, respectively, and we found no difference among treatments. Scours score and total daily score were similar for calves fed milk once or twice a day. These results suggest that feeding milk once a day can be successfully applied to a calf feeding system and that yeast products may improve structural growth.

A 100-Year Review: Calf nutrition and management

The first calf paper, published in the May 1919 issue of the Journal of Dairy Science (JDS), described factors affecting birth body weight of different breeds of calves. Other studies were done on nonmilk ingredients, growth charts were developed, and early weaning was followed to conserve milk fed to calves. Calf papers did not report use of statistics to control or record variation or to determine whether treatment means were different. Many experiments were more observational than comparative. Typically fewer than 5 calves, and sometimes 1 or 2 calves, were used per treatment. During the next 20 yr, calf studies increased and included colostrum feeding, milk and milk replacer feeding, minerals and vitamins, and fats and oils. Many concepts fundamental to current knowledge and understanding of digestion, rumen development, and milk replacer formulation were developed during this period. In addition, the concept of using antibiotic growth promoters in dairy calf diets was first evaluated and developed during the 1950s. During the 20-yr period of January 1957 through December 1976, a large number of universities in the United States and 1 in Canada contributed almost 150 papers on a variety of calf-related topics. These topics included genetics, physiology of the calf, review of calf immunity, antibiotic feeding, and milk replacer ingredients. This became the golden era of calf rumen development studies, which also engendered studies of calf starter rations and ingredients. A classic review of management, feeding, and housing studies summarized research related to calf feeding and management systems up to that point with an emphasis on maintaining calf growth and health while reducing labor and feed costs. It was also during this period that metric measurements replaced English units. In the 20-yr period from 1977 to 1996, more than 400 articles on calf nutrition and management were published in JDS. With the growing research interest in calves, a paper outlining standardized procedures for conducting and reporting data from calf experiments was first published. A very active area of calf nutrition research from the late 1970s to the mid 1980s was colostrum quality, feeding, and preservation; more than 60 such research articles were published in the journal during this time. Various nonmilk protein sources were evaluated. Extensive studies were done evaluating trace and major mineral requirements in calves along with some vitamin studies. Throughout the 1970s, 1980s, and 1990s, the primary objective of most calf research was how to wean healthy, adequately grown calves at an early age-generally less than 30 d of age. This program was reviewed in a 1979 publication. Research on calf starter ingredients, nutrient composition, and additives was minimal in the 1980s and 1990s given the importance of starter intake to the success of early weaning, but the role of water intake in starter intake and growth was established. Research on issues with calves continued to increase during the last 20-yr period as evidenced by publication of more than 580 articles in JDS as well as many more in other refereed journals. In addition to papers contributed by several universities in the United States and Canada, the number of papers authored by scientists at universities and institutes in other countries increased dramatically during this period. Factors influencing colostral antibody absorption, heat treatment of colostrum, and efficacy of colostrum supplements and replacers were reported. Most studies in this period related to nutrition. Studies were published supporting greater neonatal growth rates from feeding more milk replacer but with a higher crude protein content than traditional. Protein energy effects on growth and body composition were evaluated in concert with greater growth rates. Milk and nonmilk protein sources in milk replacers along with AA supplementation were evaluated. Limited studies were done with fat sources and fatty acid supplementation along with trace minerals and fat-soluble vitamins. Waste milk feeding and heat treatment became more prevalent. Studies established starter ingredient palatability and use of forage when fed with pelleted starters. With the advent of automatic milk and milk replacer feeders, factors influencing how and when to wean were established. Research programs established factors affecting calf behavior and welfare. Several databases were evaluated along with various published studies, and established calf growth during the first 2 mo was subsequently reflected in first- and later-lactation milk production of those calves. A new area of calf research that emerged from 1997 on was the effects of maternal environment and nutrition on calf health, growth, and future productivity. From a mechanistic standpoint, the field of epigenetics seems likely to explain many of these phenomena. Some possibilities for future calf nutrition and management were elaborated.

Exploration of the bovine colostrum proteome and effects of heat treatment time on colostrum protein profile

Heat treatment of colostrum is performed on modern dairy farms to reduce pathogenic contamination before hand-feeding the colostrum to newborn calves; however, limited data are available concerning effects of heat treatment on biologically active proteins in colostrum. The objective of this exploratory study was to investigate effects of heat treatment and length of heat treatment on colostrum protein profile. Colostrum samples were collected from Holstein cows within 12 h after parturition and assigned to the following groups: heat treatment at 60°C for 0 (untreated control), 30, 60, or 90 min. Samples were fractionated using acid precipitation, followed by ultracentrifugation and ProteoMiner (Bio-Rad Laboratories, Hercules, CA) treatment, and tandem-mass tagging was used to comparatively assess the low abundance protein profile. A total of 162 proteins were identified with more than 2 peptides in the low abundance protein enriched fraction. Of these, 62 differed in abundance by more than 2-fold in heat treated samples compared with the unheated control. The majority of proteins affected by heat treatment were involved in immunity, enzyme function, and transport-related processes; affected proteins included lactadherin, chitinase-3-like protein 1, and complement component C9. These results provide a foundation for further research to determine optimum heat treatment practices to ensure newborn calves are fed colostrum-containing proteins with the highest nutritional and biological value.

Short communication: Glucose kinetics in dairy heifers limit-fed a low- or high-forage ration at 4 levels of nitrogen intake

The objective of this research was to evaluate the effect of level of forage and N intake on glucose kinetics in growing dairy heifers. Eight Holstein heifers (beginning at 362 ± 7 kg of body weight and 12.3 ± 0.4 mo of age) were fed 8 rations according to a split-plot, 4 × 4 Latin square design with rations containing either high (75% forage dry matter) or low (25% forage dry matter) levels of forage and 4 levels of N intake (0.94, 1.62, 2.30, 2.96 g of N/kg of metabolic body weight per day). Diets were limit-fed to maintain equal predicted metabolizable energy intake over the four 28-d periods; dietary N was increased through the substitution of high-N ingredients for corn. Blood samples were collected from all heifers at times throughout d 18 to 19 to characterize glucose concentration over the course of a day, and glucose tolerance tests were conducted over the last 8 d of each period (1 heifer/d) at 4 h before feeding. Glucose concentration transiently declined after feeding for all dietary groups, but we found no evidence of a differential response over time that could be attributed to diet. When averaged over a day, glucose concentration was affected by an interaction between level of forage and N intake; however, this response appeared related more to the level of starch in the diet than to the effects of either forage or N intake per se. Early-phase kinetic response of glucose disposal after an intravenous glucose bolus was not affected by dietary treatment, which is consistent with no difference in area under the curve through 30 min. Area under the curve through 120 min tended to linearly decrease with decreasing dietary N intake. This response corresponded to the kinetic analysis, in which heifers consuming higher N intake had an attenuated return to baseline glucose levels. Additionally, heifers consuming lower N intake maintained a period of glucose concentration below baseline before returning to baseline. We concluded that the response to an intravenous glucose bolus differs in dairy heifers fed diets differing in N intake, whereas forage level did not affect this response. This should be considered when formulating rations for low N intake by replacing high-N for high-starch feedstuffs when limit-feeding dairy heifers.

Comparison of immune responses in calves fed heat-treated or unheated colostrum

Understanding the mechanisms that underlie neonatal immune function is important for appropriately treating and preventing disease. Cytokines provided in colostrum may affect immune development and function, but data describing cytokine absorption in calves and the effects of colostrum heat treatment on absorption are limited. The objectives of this experiment were to characterize immune responses in calves that received heat-treated (HT) or unheated (UH) colostrum (in terms of growth, rectal temperature, and blood cytokine and IgG concentrations) and to determine calves' ability to absorb IFNγ and IL1β from HT and UH colostrum. A single large batch of colostrum was divided to create treatments. The HT colostrum was heated to 60°C for 60 min. Both treatments were frozen until needed and warmed immediately before feeding. Bull calves (n = 26) were randomly assigned to receive 8% of their birth weight in colostrum from 1 treatment at birth. Blood was collected at 0 and 24 to 48 h after birth for IL1β, IFNγ, and IgG analyses. Subcutaneous injections of ovalbumin (5.0 mg/mL) were given at 14 and 35 ± 3 d of age. Rectal temperature and growth were monitored for 10 d following each injection. Plasma samples were collected at 0, 4, 8, and 12 h post-injection and daily for the subsequent 10 d to measure IL1β, IFNγ, and IgG concentrations. Colostrum heat treatment failed to increase blood IgG concentrations or the apparent efficiency of IgG absorption. Serum IL1β concentrations were higher in UH calves 24 to 48 h after birth and remained higher than those in HT calves through 15 d of age. Both IFNγ and IgG increased in response to ovalbumin injection; we observed no differences between treatments. Rectal temperature increased and peaked 12 h after injection at 14 and 35 d. Growth rate was reduced by exposure to the foreign antigen. Interactions of calf age and colostrum treatment with time post-injection indicate that calves tended to show greater loss in average daily gain at 35 d than at 14 d, and UH calves tended to recover greater rates of growth 6 to 10 d after receiving ovalbumin injection. Thus, feeding HT colostrum did not inhibit neonatal immune response, but it may have affected recovery from exogenous antigen challenge.

Effect of forage to concentrate ratio with sorghum silage as a source of forage on rumen fermentation, N balance, and purine derivative excretion in limit-fed dairy heifers

Sorghum silage has been shown to be a good alternative to corn silage for dairy cows; however, studies regarding heifers are insufficiently explored. Therefore, the objective of this study was to evaluate effects of changing forage to concentrate ratio (FOR:CON) in diets based on sorghum silage on N digestibility, rumen fermentation, N balance, C excretion, and microbial N yield in limit-fed dairy heifers. A split-plot 4×4 Latin square design with 19-d periods (15 d of adaptation and 4 d of sampling) was conducted with 8 rumen cannulated dairy heifers (age 13.7±0.6mo and weight 364.8±17.6kg). Heifers were fed sorghum silage-based diets with 4 FOR:CON (85:15, 75:25, 65:35, and 55:45) balanced for similar metabolizable energy intake per unit of body weight and crude protein concentration. Diets were fed to allow 900 to 1,000g/d body weight gain and were fed once daily. Total collection of feces and urine was completed on d 15 to 19 to determine N, C, urea N, allantoin, uric acid, and creatinine excretion. Rumen contents were sampled on d 19 at 0, 1.5, 3, 4.5, 6, 9, 13, 17, 21, and 23h after feeding to measure pH, volatile fatty acid (VFA), ammonia-N, and free AA concentrations. The pH decreased linearly while ammonia-N and free AA levels increased linearly with decreasing FOR:CON of diets. Although mean total VFA did not differ among treatment diets, molar proportions of VFA did. Acetate proportion decreased while propionate and butyrate increased with decreasing FOR:CON. Intake of N and urea N excretion decreased with decreasing forage proportion in diets while total N excretion, apparent N digestibility, and N retention were not different. Intake of C and excretion in feces (g/d) decreased linearly with decreasing FOR:CON in diets. Creatinine, allantoin, and uric acid excretion were not affected by FOR:CON; however, microbial N yield tended to increase linearly with greater concentrate in diets. Heifers limit fed diets based on sorghum silage demonstrated the effect of available ammonia-N and readily fermentable carbohydrates with subsequent effects on nutrient utilization when different FOR:CON were applied. Based on the presented results, FOR:CON 65:35 had the most suitable balance of available ammonia-N and readily fermentable carbohydrates for the most optimal results.

Precision-feeding dairy heifers a high rumen-degradable protein diet with different proportions of dietary fiber and forage-to-concentrate ratios

The objective of this experiment was to determine the effects of feeding a high-rumen-degradable protein (RDP) diet when dietary fiber content is manipulated within differing forage-to-concentrate ratio (F:C) on nutrient utilization of precision-fed dairy heifers. Six cannulated Holstein heifers (486.98±15.07kg of body weight) were randomly assigned to 2 F:C, low- (45% forage; LF) and high-forage (90% forage; HF) diets and to a fiber proportion sequence [33% grass hay and wheat straw (HS), 67% corn silage (CS; low fiber); 50% HS, 50% CS (medium fiber); and 67% HS, 33% CS (high fiber)] within forage proportion administered according to a split-plot, 3×3 Latin square design (16-d periods). Heifers fed LF had greater apparent total-tract organic matter digestibility coefficients (dC), neutral detergent fiber, and cellulose than those fed LC diets. Substituting CS with HS resulted in a linear reduction in dry matter, organic matter, and cellulose dC. Nitrogen dC was not different between F:C or with increasing proportions of HS in diets, but N retention tended to decrease linearly as HS was increased in the diets. Predicted microbial protein flow to the duodenum decreased linearly with HS addition and protozoa numbers HS interacted linearly, exhibiting a decrease as HS increased for LF, whereas no effects were observed for HF. Blood urea N increased linearly as HS was incorporated. The LF-fed heifers had a greater ruminal volatile fatty acids concentration. We noted a tendency for a greater dry matter, and a significantly higher liquid fraction turnover rate for HF diets. There was a linear numerical increase in the liquid and solid fraction turnover rate as fiber was added to the diets. Rumen fermentation parameters and fractional passages (solid and liquid) rates support the reduction in dC, N retention, and microbial protein synthesis observed as more dietary fiber is added to the rations of dairy heifers precision-fed a constant proportion of rumen-degradable protein.

Effect of precision feeding high- and low-quality forage with different rumen protein degradability levels on nutrient utilization by dairy heifers

One approach to improving efficiency of protein and nitrogen use for optimal productivity in dairy heifers is to provide adequate levels of protein with differing rumen degradabilities. The objective of this experiment was to determine effects of manipulating RDP in diets of dairy heifers precision fed low- and high-quality forage. Eight rumen-cannulated Holstein heifers (448 ± 19 kg BW) were randomly used and assigned to an 85% forage diet with 2 forage qualities, low quality (LQ, 48% NDF) and high quality (HQ, 38% NDF), and to 4 RDP levels (62%, 68%, 74%, and 81% of CP as RDP) within forage quality administered according to a split-plot two 4 × 4 Latin square design (20-d periods). Similar N intake was provided (1.70 g N/kg BW0.75), and alterations of RDP levels were made by exchanging canola meal with heat-treated soy protein with slow-release urea. Heifers offered the HQ diet had greater apparent total tract DM and OM digestibilities than those fed the LQ diet. Apparent N digestibility tended to be higher for the HQ diet but was not affected by the levels of RDP in diets. No difference was observed for rumen VFA concentration between forage treatments, but acetate to propionate ratio was higher for LQ-fed heifers. No difference in rumen carbohydrate fermentation was detected with increasing levels of RDP. Feeding HQ forage improved DM, OM, and N apparent digestibility. Increasing RDP in LQ and HQ had no effects on apparent digestibility of any measured parameter or N dynamics in dairy heifers.

Effect of trace minerals and starch on digestibility and rumen fermentation in diets for dairy heifers

The objective of this study was to evaluate the effect of different forms of trace minerals (TM) and the use of different starch levels in dairy heifer diets on rumen fermentation and digestibility. Eight rumen cannulated dairy heifers (15.4 ± 0.8 mo of age and 438.31 ± 18.08 kg of body weight) were subjected to a split-plot, 4 × 4 Latin square design with 19-d periods: 15d of adaptation and 4d of sampling. The whole-plot factor was type of TM; organic as proteinates (OTM) or inorganic sulfates (ITM), and the subplot was starch level (3.54, 12.95, 22.25, and 31.73%). Total collection of feces and urine was completed on d 15 to 19 to determine digestibility and TM excretion. Rumen contents were sampled on d 18 to 19 at 0, 1, 2, 4, 8, 12, 16, 20, and 22 h after feeding to measure pH and volatile fatty acid (VFA) concentrations. Plasma samples were collected to evaluate TM concentrations and enzymatic activity for ceruloplasmin, glutathione peroxidase, and superoxide dismutase. Starch level affected pH, individual VFA concentrations, and nutrient excretion. Trace mineral intake was lower for OTM compared with ITM. No effect of TM form on dry matter digestibility was detected, but as level of starch increased, diet dry matter digestibility increased. Rumen pH was lower for diets with OTM, which is consistent with higher total VFA production and butyrate proportion observed for heifers fed OTM diets. These variables may be explained by the higher bioavailability of OTM and faster utilization and fermentation by rumen microorganisms. Heifers that consumed ITM had higher moisture in feces and higher urine excretion, which increased total manure production. Total excretion of TM was not different by treatment. Blood plasma mineral concentration was not different between treatments except for Mn, which was higher for OTM. Enzymatic activity was not affected by treatments. Mineral intake was reduced and blood mineral levels were not different, suggesting enhanced absorption of OTM compared with ITM. In conclusion, based on rumen pH, VFA production, and plasma TM concentration, OTM may be more ruminally bioavailable and absorbed to a greater extent than ITM. Also, TM form affected fecal moisture and urine excretion, suggesting that ITM may stimulate water intake.

Efficiency and rumen responses in younger and older Holstein heifers limit-fed diets of differing energy density

The objective of this study was to evaluate the effects of limit feeding diets of different predicted energy density on the efficiency of utilization of feed and nitrogen and rumen responses in younger and older Holstein heifers. Eight rumen-cannulated Holstein heifers (4 heifers beginning at 257 ± 7 d, hereafter "young," and 4 heifers beginning at 610 ± 16 d, hereafter "old") were limit-fed high [HED; 2.64 Mcal/kg of dry matter (DM), 15.31% crude protein (CP)] or low (LED; 2.42 Mcal/kg of DM, 14.15% CP) energy density diets according to a 4-period, split-plot Latin square design with 28-d periods. Diets were limit-fed to provide isonitrogenous and isoenergetic intake on a rumen empty body weight (BW) basis at a level predicted to support approximately 800 g/d of average daily gain. During the last 7d of each period, rumen contents were subsampled over a 24-h period, rumen contents were completely evacuated, and total collection of feces and urine was made over 4d. Intakes of DM and water were greater for heifers fed LED, although, by design, calculated intake of metabolizable energy did not differ between age groups or diets when expressed relative to rumen empty BW. Rumen pH was lower, ammonia (NH3-N) concentration tended to be higher, and volatile fatty acids (VFA) concentration was not different for HED compared with LED and was unaffected by age group. Rumen content mass was greater for heifers fed LED and for old heifers, so when expressing rumen fermentation responses corrected for this difference in pool size, NH3-N pool size was not different between diets and total moles of VFA in the rumen were greater for heifers fed LED, whereas these pool sizes were greater for old heifers. Total-tract digestibility of potentially digestible neutral detergent fiber (NDF) was greater in heifers fed LED and for young heifers, whereas the fractional rate of ruminal passage and digestion of NDF were both greater in heifers fed LED. Digestibility of N was greater for heifers fed HED, but was unaffected by age group, whereas the efficiency of N retention was greater for heifers fed HED and for young heifers. Manure output was reduced in heifers fed HED, but the effect was largest in old heifers. Results confirm previous studies in which young heifers utilize N more efficiently than old heifers, primarily through greater efficiency of postabsorptive metabolism. Results also support the concept of limit feeding HED diets as a potential means to reduce manure excretion and increase nitrogen efficiency.

Straw particle size in calf starters: Effects on digestive system development and rumen fermentation

Two trials were conducted to determine effects of straw particle size in calf starter on rumen fermentation and development in calves. Holstein calves (n = 17 in trial 1; n = 25 in trial 2) were housed in individual pens; bedding (wood shavings) was covered with landscape fabric to completely avoid consumption of bedding. Milk replacer was fed at 12% of birth body weight per day and water offered free choice. Calves were randomly assigned to 4 treatments differing in geometric mean particle length (X_gm) of straw comprising 5% of starter dry matter. Straw was provided within the pellet at manufacture (PS; 0.82 mm X_gm) or mixed with the pellet at time of feeding at X_gm of 3.04 (SS), 7.10 (MS), or 12.7 (LS) mm. Calves (n = 12; 3/treatment) in trial 1 were fitted with a rumen cannula by wk 2 of age. A fixed amount of starter that was adjusted with age and orts were fed through the cannula in cannulated calves. Calves were euthanized 6 wk after starter was offered (9 and 7 wk of age for trials 1 and 2, respectively). Rumen digesta pH linearly decreased with age, whereas volatile fatty acid concentration increased with age. Overall pH had a cubic trend with SS lower than that of PS and MS. Molar proportion of acetate decreased with age whereas propionate proportion increased. Overall molar proportions of volatile fatty acids were not affected by diet. Fecal X_gm was not different in spite of changes in diet particle size and rumen digesta of PS being greater than SS, MS, and LS at slaughter. Fecal pH and starch concentration were not affected by diet; however, pH decreased whereas starch content increased with age. Weight of stomach compartments, rumen papillae length and width, and rumen wall thickness did not differ between diets. Omasum weight as a percentage of body weight at harvest linearly decreased as straw particle size increased. Under the conditions of this study, modifying straw particle length in starter grain resulted in minimal rumen fermentation parameter changes and no changes in rumen development. Rumen pH and fermentation changes with age were likely effects of increasing starter intake.

Effect of forage level and replacing canola meal with dry distillers grains with solubles in precision-fed heifer diets: Digestibility and rumen fermentation

Objectives of this study were to determine the effects of feeding differing forage-to-concentrate ratios (F:C) and inclusion rates of corn dry distillers grain with solubles (DDGS) on digestion and rumen fermentation in precision-fed dairy heifer rations. A split-plot design with F:C as whole plot and DDGS inclusion level as sub-plot was administered in a 4-period (19 d) 4 × 4 Latin square. Eight rumen-cannulated Holstein heifers (12.5 ± 0.5 mo of age and 344 ± 15 kg of body weight) housed in individual stalls were allocated to 2 F:C [50:50, low forage, or 75:25 high forage; dry matter (DM) basis] and to a sequence of DDGS inclusion (0, 7, 14, and 21%; DM basis). Forage was a mix of 50% corn silage and 50% grass hay (DM basis). Diets were fed to allow for 800 g/d of body weight gain and fed 1×/d. Rumen contents were sampled at -2, 0, 2, 4, 6, 8, 10, 12, and 20 h after feeding for rumen fermentation measures. Low-forage rations had greater DM and organic matter apparent digestibility. We detected a quadratic effect for DM, organic matter, acid detergent fiber, and neutral detergent fiber apparent digestibility, with the 14% DDGS inclusion level having the highest values. Nitrogen retention decreased with increasing levels of DDGS. Molar proportions of acetate tended to be greater for HF and decreased as DDGS increased; propionate increased as DDGS increased, resulting in the opposite effect on acetate to propionate ratio. Rumen protozoa count decreased as DDGS increased. Moderate levels (14% of DM) of DDGS appear to enhance nutrient utilization and fermentation in precision-fed dairy heifers fed different F:C diets.

Digestive development in neonatal dairy calves with either whole or ground oats in the calf starter

A series of 3 trials was conducted to determine effects of whole or ground oats in starter grain on reticulorumen fermentation and digestive system development of preweaned calves. Male Holstein calves (43.1±2.3kg at birth; n=8, 9, and 7 for trials 1, 2, and 3, respectively) were housed in individual pens in a heated facility; bedding was covered with landscape fabric to prevent consumption of bedding by the calves. In trials 1 and 2 only, calves were fitted with rumen cannulas by wk 2 of life. In all trials, a fixed amount of starter (containing 25% oats either ground and in the pellet or whole) was offered daily; orts were fed through the cannula in trials 1 and 2. Calves were randomly assigned to an all-pelleted starter or pellets plus whole oats. Rumen contents (trials 1 and 2) were sampled weekly at -8, -4, 0, 2, 4, 8, and 12 h after grain feeding for determination of pH and volatile fatty acids. Calves were killed 3 wk (trial 1) or 4 wk (trials 2 and 3) after grain was offered; organs were harvested, emptied, rinsed, and weighed to gauge digestive organ development. Starter intake was not different between treatments. Weekly measurements of rumen digesta pH did not change and only subtle changes were observed in molar proportions of individual volatile fatty acids. Molar proportion of butyrate and pH linearly decreased with age, whereas acetate proportion increased. Reticulorumen weight and papillae length tended to be greater for calves fed pelleted starter, whereas abomasum weight was greater for calves fed pellets plus whole oats. Fecal particle size and starch content were greater for calves fed pellets plus whole oats. Under the conditions of this study, physical form of oats in starter grain did not affect rumen fermentation measurements; greater rumen weight and papillae length in calves fed pelleted starter may be the result of greater nutrient availability of ground oats. Under the conditions of this study with young calves on treatments for <4 wk, increasing particle size of the starter by feeding whole oats did not affect rumen fermentation nor did it improve digestive system development.

Saccharomyces cerevisiae live culture affects rapidly fermentable carbohydrates fermentation profile in precision-fed dairy heifers

Lascano, G. J., Heinrichs, A. J. and Tricarico, J. M. 2015. Saccharomyces cerevisiae live culture affects rapidly fermentable carbohydrates fermentation profile in precision-fed dairy heifers. Can. J. Anim. Sci. 95: 117–127. The experimental objective was to determine the dose effect of live yeast culture (YC) on rumen fermentation profiles and microbial total cell concentrations in precision-fed dairy heifers exposed to different rapidly fermented carbohydrates diets. A split-plot design with starch level as the whole plot and YC dose as sub-plot was administered in a four-period (21 d) 4×4 Latin square balanced for carryover effects. Eight Holstein heifers were allocated to two starch treatments (28% starch: HS; 17% starch: LS) and to a sequence of YC doses (0, 10, 30, and 50 g d−1). Total volatile fatty acid concentration was not different among YC doses or starch level, but molar proportions of propionate, isobutyrate, and isovalerate were higher for HS than for LS. Mean ruminal ammonia concentration was increased in HS-fed heifers. Heifers fed HS had an increased number of viable, non-viable, and total fluid-associated bacteria, particle-associated bacteria, and total bacteria. Increasing YC dose linearly beyond 10 g d−1 decreased viable and total fluid-associated bacteria. The effects of various YC doses on ruminal fermentation products, pH, and microbial total cell concentrations indicate diet dependency between source of readily available carbohydrates and YC addition in dairy heifers.

Feeding lactating dairy cattle long hay separate from the total mixed ration can maintain dry matter intake during incidents of low rumen pH

The objective of this study was to investigate effects of offering dry hay of different quality and length on rumen pH and feed preference in lactating dairy cows. Eight rumen-cannulated Holstein cows (104 ± 34 d in milk, body weight of 601 ± 116 kg, and parity of 2.38 ± 1.69; mean ± standard deviation) were used in a replicated 4 × 4 Latin square design. Each period encompassed 21 d divided into 5 phases: adaptation (d 1 to 14), with ad libitum total mixed ration (TMR); baseline (d 15 to 17), with ad libitum TMR; restricted feeding (d 18), with cows fed for 75% of baseline dry matter intake; challenge (d 19), with 4 kg (as-fed) of finely ground wheat mixed into the digesta of each cow via rumen cannula before feeding; and recovery (d 20 to 21), with ad libitum TMR. Cows were assigned to squares by parity and randomly assigned to treatments. Treatments were 5.2% low-quality hay TMR (CL), 5.2% high-quality hay TMR (CH; both hays were chopped and included in TMR), TMR with 5.2% supplemental long low-quality hay (TMR+L), and TMR with 5.2% supplemental long high-quality hay (TMR+H; both hays were unprocessed and fed separate from TMR).Low-quality hay contained 8.6% crude protein and 67.1% neutral detergent fiber, whereas high-quality hay contained 14.4% crude protein and 56.2% neutral detergent fiber. Animals were housed individually, milked twice per day, and fed once per day for 10% refusal rate. Data were analyzed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Subacute ruminal acidosis challenge decreased weighted average rumen pH from 5.72 to 5.51. Cows fed TMR+L had higher rumen pH compared with CL and TMR+H on d 19. During d 20, cows fed chopped hay had higher rumen pH than cows fed supplemental long hay. Cows fed supplemental long hay had greater dry matter intake during baseline and challenge days compared with when hay was chopped and included in the TMR. Minimal differences among diets were found for TMR particle size selection during the challenge day; however, cows had a greater preference for high-quality long hay during recovery days. Milk production averaged 38.3 kg/d and did not differ among treatments. Fat, protein, and lactose yields were also not different among treatments. Milk fatty acid profile was altered by treatment. The TMR+L and CH treatments increased production of cis-9,trans-11 conjugated linoleic acid. Results of this study indicate that feeding TMR plus supplemental long hay can maintain dry matter intake during incidents of and recovery from periods of low ruminal pH.

Heat treatment of colostrum increases immunoglobulin G absorption efficiency in high-, medium-, and low-quality colostrum

Previous studies with heat-treated colostrum fed to neonatal calves have consistently used average-quality colostrum. Studies have not compared colostrum across a range of immunoglobulin levels. This study was conducted to investigate IgG absorption in neonatal dairy calves using colostrum of various qualities. Colostrum from the Pennsylvania State University dairy was collected over 2 yr and sorted into high, medium, and low quality based on colostrometer measurement. Colostrum within each category was pooled to create 3 unique, uniform batches. Half of each batch was frozen to be fed without heat treatment. The second half of each batch was heat treated at 60°C for 30min. This process was conducted in September 2011, and repeated in June 2012. Colostrum treatments were analyzed for standard plate count, coliforms, noncoliform gram-negative bacteria, and total IgG concentration. Plasma samples were collected from 145 calves 48h after birth and analyzed for IgG1, IgG2, total protein, and hematocrit. Colostrum quality (high, medium, or low), treatment (unheated or heat treated), and their interactions were analyzed as fixed effects, with year included as a random effect. Heat treatment significantly reduced all types of bacteria and IgG concentration. Plasma IgG concentration at 48h increased linearly with the concentration of IgG in the colostrum that was consumed. Heat treatment of colostrum increased plasma IgG concentration by 18.4% and apparent efficiency of absorption by 21.0%. Results of this study suggest that heat treatment of colostrum containing approximately 50 to 100mg IgG/mL increases absorption of IgG from colostrum.

Identifying efficient dairy heifer producers using production costs and data envelopment analysis

During November and December 2011, data were collected from 44 dairy operations in 13 Pennsylvania counties. Researchers visited each farm to collect information regarding management practices and feeding, and costs for labor, health, bedding, and reproduction for replacement heifers from birth until first calving. Costs per heifer were broken up into 4 time periods: birth until weaning, weaning until 6 mo of age, 6 mo of age until breeding age, and heifers from breeding to calving. Milk production records for each herd were obtained from Dairy Herd Improvement. The average number of milking cows on farms in this study was 197.8 ± 280.1, with a range from 38 to 1,708. Total cost averaged $1,808.23 ± $338.62 from birth until freshening. Raising calves from birth to weaning cost $217.49 ± 86.21; raising heifers from weaning age through 6 mo of age cost $247.38 ± 78.89; raising heifers from 6 mo of age until breeding cost $607.02 ± 192.28; and total cost for bred heifers was $736.33 ± 162.86. Feed costs were the largest component of the cost to raise heifers from birth to calving, accounting for nearly 73% of the total. Data envelopment analysis determined that 9 of the 44 farms had no inefficiencies in inputs or outputs. These farms best combined feed and labor investments, spending, on average, $1,137.40 and $140.62/heifer for feed and labor. These heifers calved at 23.7 mo of age and produced 88.42% of the milk produced by older cows. In contrast, the 35 inefficient farms spent $227 more on feed and $78 more on labor per heifer for animals that calved 1.6 mo later and produced only 82% of the milk made by their mature herdmates. Efficiency was attained by herds with the lowest input costs, but herds with higher input costs were also able to be efficient if age at calving was low and milk production was high for heifers compared with the rest of the herd.

Effects of feeding different levels of dietary fiber through the addition of corn stover on nutrient utilization of dairy heifers precision-fed high and low concentrate diets

The objective of this experiment was to assess the effects of manipulating dietary fiber by replacing corn silage (CS) with lower quality forage as corn stover (CST) when used in high concentrate (HC) and low concentrate (LC) diets for precision-fed dairy heifers. Eight Holstein heifers (335.6 ± 7.41 kg of body weight) were randomly assigned to 2 levels of concentrate: HC (20% forage) and LC (80% forage), and to a forage type sequence [0% of forage as corn stover (CST), 100% corn silage (CS); 20% CST, 80% CS; 40% CST, 60% CS; and 60% CST, 40% CS] within concentrate level administered according to a split-plot, 4 × 4 Latin square design (21-d periods). Heifers fed HC had higher apparent total-tract dry matter digestibility (DMD). Increasing the fiber level by increasing the amount of CST in the diet resulted in a linear decrease of DMD and organic matter digestibility. Heifers fed LC diets had higher neutral detergent fiber (NDF) digestibility and tended to have lower acid detergent fiber (ADF) digestibility than those fed HC diets. Substituting CS with 20% CST resulted in the highest NDF and ADF digestibilities. Digestibility of N was not different, but N retention increased for HC and decreased quadratically for LC diets. Heifers fed HC diets decreased fecal output, and CST linearly increased these parameters. Urine volume tended to be higher for HC-fed heifers, and increasing dietary fiber through CST inclusion tended to decrease urine output. This shift in water excretion resulted in similar total manure output. Total purine derivative excretion did not differ between treatments, but interacted with CST addition, resulting in a linear increase in microbial protein flow to the duodenum in HC-fed heifers and in a linear decrease in LC diets as CST increased. In conclusion, increasing dietary fiber through CST decreased DMD and organic matter digestibility linearly, whereas NDF and ADF digestibility were maximized when 20% CST was added to HC and LC diets. Microbial protein synthesis increased and decreased linearly with CST addition in HC and LC diets, respectively. Retention of N increased and decreased quadratically with CST addition in HC and LC diets, respectively. Total manure excretion was not different between HC or LC diets.

Evaluation of calf milk pasteurization systems on 6 Pennsylvania dairy farms

Waste milk has been fed to calves for many years, but concerns with bacterial contamination as well as possible transmission of diseases have discouraged widespread use of this feed. Pasteurization of waste milk is one option to reduce management risk while utilizing a valuable, low-cost, liquid feed source for calves. However, many farms currently pasteurizing waste milk lack a system to adequately monitor the efficiency of the process. A study was carried out to evaluate 6 on-farm pasteurization systems, including high-temperature, short-time pasteurizers and low-temperature, batch pasteurizers. Milk samples were taken pre- and postpasteurization as well as from the calf buckets and immediately frozen for later bacterial culture. Samples were collected twice daily for 15 d. Milk samples were examined for standard plate count (SPC), coagulase-negative staphylococci count, environmental streptococci count, coliform count, gram-negative noncoliform count, Streptococcus agalactiae count, and Staphylococcus aureus count. Before pasteurization, 68% of the samples had SPC <20,000 cfu/mL, and 39% of samples contained <100 cfu/mL of coliform bacteria. After pasteurization, 96% of samples had SPC <20,000 cfu/mL, and 92% had coliform counts <100 cfu/mL. Bacteria counts were significantly reduced by pasteurization, and pasteurized milk contained acceptable numbers of bacteria in >90% of samples. These results indicate that pasteurization can be very effective in lowering bacterial contamination of milk. However, bacteria numbers significantly increased after pasteurization and, in some cases, bacteria counts in milk fed to calves were similar to prepasteurization levels. Milk handling after pasteurization was identified as an important issue on the farms studied.

Effect of feed sorting on chewing behavior, production, and rumen fermentation in lactating dairy cows

Ration sorting is thought to allow cows to eat different rations throughout the day, causing fluctuations in rumen fermentation patterns that can be detrimental to production and possibly animal health. The objective of this experiment was to study the effects of varying total mixed ration (TMR) particle size on sorting behavior of lactating dairy cows and to evaluate effects on chewing behavior, milk yield, milk components, and rumen fermentation. Eight multiparous, Holstein cows (90±32 d in milk; 4 rumen cannulated) were randomly assigned to replicated 4×4 Latin squares. Cows were fed diets that varied in the chop length of dry grass hay. The diet consisted of 29.4% corn silage, 22.9% ground corn, 17.6% alfalfa haylage, and 11.8% dry grass hay on a dry matter basis. The percentage of hay particles >26.9 mm was 4.2, 34.1, 60.4, and 77.6% for the short (S), medium (M), long (L), and extra long (XL) hays, respectively. This resulted in the TMR of each diet having 1.5 (S), 6.5 (M), 8.6 (L), and 11.7% (XL) of particles >26.9 mm. Daily ruminating time [19.3, 19.2, 22.4, and 21.3 min/kg of dry matter intake (DMI) for S, M, L, and XL] and eating time (13.9, 14.6, 17.2, and 16.1 min/kg of DMI for S, M, L, and XL) increased linearly as TMR particle size increased. Daily DMI decreased linearly as TMR particle size increased and was 26.9 (S), 27.0 (M), 24.1 (L), and 25.1 (XL) kg/d. No differences were found in rumen volatile fatty acids and NH(3), and only slight changes were found in rumen pH. Milk production and milk components were also similar among diets. Despite large differences in particle size among these diets and certain chewing and ruminating differences, no changes in rumen fermentation, milk production, or milk components were found in this study.

Technical note: Evaluation of procedures for analyzing ration sorting and rumen digesta particle size in dairy cows

Collecting total mixed ration (TMR) samples throughout the day to measure sorting activity of dairy cows may cause changes to the sorting behavior of cows or may make it more difficult to elucidate effects of sorting on TMR particle size distributions. Also, forage particle size research commonly includes analysis of the solid portion of rumen digesta for particle size distribution after digesta has been squeezed through several layers of cheesecloth. Therefore, the first objective of this experiment was to determine if collecting TMR samples throughout the day affected sorting behavior of cows and resulted in a different particle size distribution than when TMR was not artificially altered during the day. The second objective of this experiment was to determine if squeezing rumen digesta samples through cheesecloth changed particle size distribution when analyzed by a wet sieving technique. It was determined that small, significant differences existed in particle size distribution between the 2 sampling methods of TMR for sorting behavior. These differences were more likely to occur at time points later in the day. This resulted in small changes in sorting indices calculated from these data; sampling and mixing TMR throughout the day reduced the degree of sorting. Squeezing rumen digesta through 4 layers of cheesecloth had no effect on particle size distribution of particles >0.15 mm but reduced the amount of rumen fluid-associated dry matter contained in the sample.

Technical note: A noninvasive urine collection device for female cattle: modification of the urine cup collection method

Total urine collection from female cattle requires the use of indwelling urinary catheters or an external device requiring secure attachment with adhesive to the animal; neither method is ideal for the welfare of the cattle. A urine collection device was developed to enable total urine collection in female dairy cattle without the use of adhesive to attach the device to the vulva of the animal; the device was a modification of one described previously for female cattle. The urine collection device was made from polypropylene with maximum dimensions (height x width x depth) of 17.5 x 11.0 x 6.0 cm and an opening of approximately 42 cm(2) to cover the vulva. The device was secured using a commercially available udder support harness that provided snap-fasteners and support for the device to be positioned at the level of the vulva. At the point of attachment, a metal brace surrounded the device and was connected to the udder support by metal rings, which kept the urine cup in proper position as the animal arched to urinate. A metal O-clamp and pieces of rubber, serving as leak-proof washers, connected the bottom of the device to Gooch tubing. Another metal clamp was attached to a polyvinyl chloride adapter that was connected to a rubber hose, and urine was collected into carboys located on the floor approximately 1.5 m behind the animals. This modification of a urine cup allows several noninvasive total feces and urine collection studies of unrestricted length to be undertaken without the use of adhesive to attach the device. The floor-level collection system is a practical, portable, and handy system that will permit researchers to perform nutrient balance and metabolic studies on female cattle.

Effect of heat treatment of bovine colostrum on bacterial counts, viscosity, and Immunoglobulin G concentration

A study was conducted to identify the optimal temperature and time at which heat treatment of bovine colostrum would least change viscosity and IgG concentrations yet reduce bacterial count. First-milking colostrum with >50g of immunoglobulins/L (measured by colostrometer) was collected from 30 Holstein cows. Aliquots of colostrum were heated for 0, 30, 60, or 90min at 57, 60, or 63 degrees C in a water bath. Samples were examined for viscosity, IgG(1), and IgG(2) concentrations, standard plate count, coagulase-negative staphylococci, environmental streptococci, coliform, gram-negative noncoliform, Streptococcus agalactiae, and Staphylococcus aureus counts. All heat treatments reduced counts of all bacteria groups measured compared with untreated colostrum samples. Heat treatment at >or=60 degrees C denatured IgG(1) compared with untreated colostrum; however, colostral IgG(2) levels were not reduced when temperature was held at 60 degrees C for <60min. Viscosity was not affected when temperature was held at 60 degrees C for <60min. In this study, heat treatment of bovine colostrum at 60 degrees C for 30 or 60min reduced bacterial count, slightly reduced IgG concentration, and did not affect viscosity.

Feeding heat-treated colostrum or unheated colostrum with two different bacterial concentrations to neonatal dairy calves

The objective of this study was to determine the effects of feeding heat-treated colostrum or unheated colostrum of different bacterial counts on passive transfer of immunity in neonatal dairy calves. First milking colostrum was collected from Holstein cows, frozen at -20 degrees C, and then thawed and pooled into a single batch. One-third of the pooled colostrum was transferred into plastic containers and frozen at -20 degrees C until needed for feeding (unheated-low bacteria). Another third was heat-treated at 60 degrees C for 30 min and then frozen at -20 degrees C until needed for feeding (heat-treated). The final third of colostrum was transferred into plastic containers, stored at 20 degrees C for bacteria to grow for 24 h (unheated-high bacteria), and then frozen at -20 degrees C until needed for feeding. A total of 30 Holstein bull calves weighing >or=30 kg at birth were systematically enrolled into 1 of the 3 treatment groups. Calves were separated from their dams at birth before suckling occurred. Before colostrum was fed, a jugular blood sample was collected from each calf. The first feeding consisted of 3.8 L of colostrum containing, on average, 68 g of IgG/L using an esophageal feeder between 1.5 and 2 h after birth. For the second and third feeding pasteurized whole milk at 5% of birth weight was fed. Blood samples were collected before colostrum feeding and at 24 and 48 h of age to determine serum total protein (STP) and IgG concentrations. Heat treatment of colostrum at 60 degrees C for 30 min reduced colostrum bacteria concentration yet maintained colostral IgG concentration and viscosity at similar levels to the control treatment. Calves fed heat-treated colostrum had significantly greater STP and IgG concentrations at 24 h and greater apparent efficiency of absorption (AEA) of IgG (STP = 62.5 g/L; IgG = 26.7 g/L; AEA = 43.9%) compared with calves fed unheated-low bacteria colostrum (STP = 57.0 g/L; IgG = 20.2 g/L; AEA = 35.4%) or unheated-high bacteria colostrum (STP = 56.2 g/L; IgG = 20.1 g/L; AEA = 32.4%). High bacteria load in colostrum did not interfere with total protein or IgG absorption or AEA.

Feeding heat-treated colostrum to neonatal dairy heifers: effects on growth characteristics and blood parameters

Newborn Holstein heifer calves were studied to compare absorption of immunoglobulin G (IgG(1) and IgG(2)), total serum protein concentration, lymphocyte counts, health scores, growth, and starter intake after receiving unheated or heat-treated colostrum. First-milking colostrum was collected from Holstein cows and frozen at -20 degrees C to accumulate a large batch. After thawing and mixing, half of the colostrum was transferred into 1.89-L plastic containers and frozen at -20 degrees C until needed for feeding. The remaining half was heated at 60 degrees C for 30 min, transferred into 1.89-L plastic containers, and then frozen at -20 degrees C until needed for feeding. Forty heifer calves weighing > or =32 kg at birth were enrolled into 1 of 2 treatment groups before suckling occurred. For the first feeding, 3.8 L of colostrum was bottle fed by 1.5 to 2 h of age. For the second and third feedings, pasteurized whole milk at 5% of birth body weight (BW) was fed. Subsequently, calves received milk replacer containing 20% crude protein and 20% fat at 10% of birth BW/d until wk 5. Milk replacer was reduced to 1 feeding of 5% birth BW until weaning at 6 wk of age. Blood samples and growth data were collected through wk 8. Batch heat-treatment of colostrum at 60 degrees C for 30 min lowered colostrum bacteria concentration while maintaining colostral IgG concentration and viscosity. Calves fed heat-treated colostrum had significantly greater IgG concentrations at 24 h and greater apparent efficiency of IgG absorption (IgG = 23.4 g/L; apparent efficiency of absorption = 33.2%) compared with calves fed unheated colostrum (IgG = 19.6 g/L; apparent efficiency of absorption = 27.7%). There was no difference between treatment groups in growth measurements, calf starter intake, lymphocyte counts, or health scores.

Effects of nucleotide supplementation in milk replacer on small intestinal absorptive capacity in dairy calves

Milk replacer was supplemented with nucleotides and fed to dairy calves from birth through weaning to examine the potential for enhancing recovery of small intestinal function after enteric infection. Three treatments of 23 calves each were fed milk replacer (10% body weight/d) supplemented with no nucleotides (C), purified nucleotides (N), or nucleotides from an extract of Saccharomyces cerevisiae (S). Average daily gain, health scores, fecal dry matter, and fecal bacteria were monitored, and blood was analyzed for packed cell volume, glucose, blood urea nitrogen (BUN), and creatinine. Calves were monitored twice daily for fecal score, and 48 h after increased fecal fluidity was recorded, intestinal function was evaluated by measuring absorption of orally administered xylose (0.5 g/kg of body weight). Packed cell volume of blood was greater for treatment N for wk 2 and 5 compared with other treatment groups. Four calves per treatment were killed, and intestinal tissue was evaluated for morphology, enzyme activities, and nucleoside transporter mRNA expression. Treatment S calves had increased abundance of nucleoside transporter mRNA, numerically longer villi, and lower alkaline phosphatase than other groups. Growth measurements and plasma concentrations of glucose, BUN, creatinine, and IgG were not different between treatments; however, BUN-to-creatinine ratio was higher for treatment N, possibly indicating decreased kidney function. There were also no treatment effects on fecal dry matter and fecal bacteria population. However, N-treated calves had the highest detrimental and lowest beneficial bacteria overall, indicating an unfavorable intestinal environment. Supplementation of purified nucleotides did not improve intestinal morphology or function and resulted in higher fecal water loss and calf dehydration. Supplementation of nucleotides derived from yeast tended to increase calf intestinal function, provide a more beneficial intestinal environment, and improve intestinal morphology.

A survey of bovine colostrum composition and colostrum management practices on Pennsylvania dairy farms

Colostrum composition and management were surveyed via sample and data collection from 55 dairy farms in Pennsylvania. Colostrum samples were analyzed for fat, protein, lactose, total solids, ash, Ig, lactoferrin, water- and fat-soluble vitamins, and minerals. Mean percentages of fat, protein, and lactose in colostrum were 6.7, 14.9, and 2.5, respectively. Concentrations of IgG1, IgG2, IgA, IgM, and lactoferrin were 35.0, 6.0, 1.7, 4.3, and 0.8 mg/mL, respectively. Mean concentrations of fat-soluble vitamins, including retinol, tocopherol, and beta-carotene, were 4.9, 2.9, and 0.7 microg/g, respectively. Mean concentrations of water-soluble vitamins were 0.34, 0.90, 4.55, 0.60, 0.15, 0.21, and 0.04 microg/mL for niacin, thiamine, riboflavin, vitamin B12, pyridoxal, pyridoxamine, and pyridoxine, respectively. Mean concentrations (mg/kg) of selected minerals in colostrum were also determined (Ca 4,716; P 4,452; Mg 733; Na 1,058; K 2,845; Zn 38; Fe 5.3; Cu 0.3; S 2,595; and Mn 0.1). The findings of this study revealed that the mean concentrations of most nutrients in colostrum have increased when compared with values previously reported. Results also showed that management practices have improved over time, particularly with regard to colostrum storage and feeding. Additionally, we observed that herd size influenced colostrum management and quality. It can be inferred, based on these findings, that although improvements have been made with regard to colostrum management and quality, there is still a need to educate producers on issues related to storage and timely feeding of colostrum to increase passive transfer and decrease the rate of calf morbidity and mortality.

The Effects of Controlled Feeding of a High-Forage or High-Concentrate Ration on Heifer Growth and First-Lactation Milk Production

The objective of this experiment was to evaluate growth and first-lactation milk production in dairy heifers fed a high-forage (HF) or high-concentrate (HC) ration for similar levels of average daily gain (ADG) before puberty. Responses in weight and structural gains were determined on 41 Holstein heifers fed diets containing the same ingredients but formulated in different proportions to give 2 treatment rations of 75% forage or 75% concentrate. The feeding period lasted 245 d, and individual animal dry matter intake was controlled to maintain constant ADG between diets. Puberty was assessed, and first-lactation milk production was evaluated through 150 d. Average dry matter intakes required to achieve desired levels of gain were 5.96 HF and 5.32 HC kg/d (SE +/- 0.12), and the associated feed efficiency (kg of ADG/kg of dry matter intake) was 0.142 HF and 0.156 HC (SE +/- 0.003) over the experimental growth period. Throughout the feeding period, ADG was not affected by treatment (0.828 HF vs. 0.827 HC; SE +/- 0.010 kg/d). Gains in structural measurements were not affected by treatment with the exception of paunch girth, which increased faster in HC-fed heifers. Body weight at puberty (293 HF vs. 287 HC; SE +/- 7 kg) and experimental ADG prior to puberty (0.837 HF vs. 0.837 HC; SE +/- 0.009 kg/d) were not different between rations. Milk and component production were numerically greater for heifers fed HC prior to puberty, although only fat-corrected milk and fat production were significant. From the results of this experiment we conclude that, compared with heifers fed HF for equal ADG, feeding dairy heifers HC before puberty did not affect most structural growth characteristics or puberty attainment and allowed equal or improved 150-d milk and component production. Controlled feeding of HC during the rearing period may allow for improved growth efficiency for dairy heifers while maintaining future productivity.

Variability in Holstein heifer heart-girth measurements and comparison of prediction equations for live weight

Measurement of heart-girth (chest circumference) is commonly used to estimate dairy heifer body weight from previously derived equations or tables. In this experiment, variability of heart-girth measurements as they are taken in the field was analyzed to determine the standard deviation within a group of 26 Holstein heifers of various ages weighing 42-590 kg. Standard deviations were 2.19 cm among 26 observers and 2.74 cm within any one observer. Repeatability between two heart-girth measurements by an individual observer on the same animal using a blind heart-girth tape was >0.99. Correlation coefficients between two measurements by different observers using blind measuring tapes on the same animal also were >0.99, with 99% of total differences due to observer and heifer, indicating very little random variation. A second part of this study was the validation of the most recently derived equation to calculate body weight from heart-girth. The equation was validated with data sets from universities across the United States and field data collected specifically for this study. Experimental and field data comprised of heart-girth and body weight measurements upheld the previously derived equation and support its continued use. These results allow more precise interpretation of heart-girth data collected from field studies with Holstein dairy heifers and provide more complete validation of existing body weight-prediction equations.