Growth, body composition, and visceral organ mass and metabolism in lambs during and after metabolizable protein or net energy restrictions

Effects of dietary niacinamide and CP concentrations on the nitrogen excretion, growth performance, and meat quality of pigs

Reducing the dietary CP concentration in the formulation of low-protein diets without adverse effects on animal growth performance and meat quality remains challenging. In this study, we investigated the effects of nicotinamide (NAM) on the nitrogen excretion, growth performance, and meat quality of growing-finishing pigs fed low-protein diets. To measure the nitrogen balance, we conducted two trials: in nitrogen balance trial 1, four crossbred (Duroc × Landrace × Large White) barrows (40 ± 0.5 kg BW) were used in a 4 × 4 Latin square design with four diets and periods. The diets consisted of a basal diet + 30 mg/kg NAM (a control dose), basal diet + 90 mg/kg NAM, basal diet + 210 mg/kg NAM, and basal diet + 360 mg/kg NAM. In nitrogen balance trial 2, another four barrows (40 ± 0.5 kg BW) were used in a 4 × 4 Latin square design. The diets consisted of a basal diet + including 30 mg/kg NAM (control), basal diet + 360 mg/kg NAM, low-protein diet + 30 mg/kg NAM, and low-protein diet + 360 mg/kg NAM. To measure growth performance, two trials were conducted. In growth performance trial 1, 40 barrows (37.0 ± 1.0 kg) were randomly allocated to one of four dietary treatments (n = 10 per group), whereas in growth performance trial 2, 300 barrows (41.4 ± 2.0 kg) were randomly allocated to one of four dietary treatments, with each dietary treatment conducted in five repetitions with 15 pigs each. The four diets in the two growth performance trials were similar to those in nitrogen balance trial 2. Supplementing the diet with 210 or 360 mg/kg NAM reduced urinary nitrogen excretion and total nitrogen excretion and increased nitrogen retention comparted with the control diet (P < 0.05). Compared with the control diet, the low-protein diet with 360 mg/kg NAM reduced faecal, urinary, and total nitrogen excretion (P < 0.05) without affecting nitrogen retention and average daily gain (P > 0.05). Pigs fed the low-protein diet with 360 mg/kg NAM showed a decreased intramuscular fat content in the longissimus thoracis muscle when compared with pigs fed the control diet (P > 0.05). Our results suggest NAM as a suitable dietary additive to reduce dietary CP concentration, maximise nitrogen retention and growth performance, and decrease fat deposition in pigs.

Assessment of Equations to Predict Body Weight and Chemical Composition in Growing/Finishing Cattle and Effects of Publication Year, Sex, and Breed Type on the Deviation from Observed Values

Body weight and chemical composition are important aspects of beef cattle nutrition and management; however, existing equations estimating relationships among empty body and carcass chemical components were developed over 40 years ago using different cattle genetics and production systems. The objective of this analysis was to evaluate existing equations in predicting empty body and carcass chemical composition and determine the effect of sex, breed type, and publication year. A dataset was developed from published literature that contained 388 treatment means from 46 studies published between 1970 and 2020. Two equations relating shrunk body weight (SBW) to empty body weight (EBW), and 8 equations relating EBW and hot carcass weight (HCW) were found in the literature and evaluated using the developed dataset. Three sets of equations relating empty body chemical components, 4 sets of equations relating carcass chemical components, and 2 sets of equations relating carcass with empty body chemical components were found in the literature and evaluated using the dataset. Precision and accuracy of the equations were evaluated by simple linear regression of observed on predicted values, mean bias (MB), and concordance correlation coefficient (CCC). Additionally, the fixed effects of publication year, sex, and breed type on the deviation from observed values were evaluated using a general linear model. Both equations relating SBW to EBW and all equations relating EBW to HCW had high precision, but accuracy varied from -3.22 to -0.11% and -9.35 to -3.73% MB, respectively, and all the equations were affected by sex and breed type with 8 out of the 10 equations affected by publication year. For prediction of empty body chemical composition assuming empty body water is known, the 3 sets of equations varied in precision for protein (0.18 to 0.46), but not for fat (0.88 to 0.96) or ash (0.06 to 0.13) based on CCC, although the precision of prediction of protein and ash were poor. Accuracy of the 3 sets of equations varied for predicting empty body fat, protein, and ash with MB of -19.73 to -3.81, 1.67 to 15.91, and -0.16 to 15.75%, respectively. All 3 sets of equations were affected by publication year and breed type for predicting empty body fat, protein, and ash, and by sex for ash. For prediction of carcass chemical components assuming carcass water is known, the precision was similar among the 4 sets of equations for predicting fat (0.92 to 0.95), protein (0.34 to 0.40), and ash (-0.02 to -0.01) based on CCC, although precision was poor for protein and ash, but accuracy varied for prediction of carcass fat, protein and ash with MB of -11.20 to -2.52, 2.72 to 8.92, and -4.66 to 20.12%, respectively. Publication year and breed type affected the prediction of carcass fat and protein, and publication year, sex, and breed type affected the prediction of carcass ash for all 4 sets of equations. The precision of predicting empty body chemical components assuming carcass chemical components are known was high for water (0.96 and 0.98), fat (0.97 and 0.98), protein (0.97 and 0.97), and ash (0.98 and 0.96) and similar between the 2 sets of equations based on CCC. The accuracy of predicting empty body water (-1.68 and -0.33%), fat (6.38 and 2.70%), protein (0.85 and -0.54%), and ash (-0.65 and -4.54%) was moderate to high, but differed between sets of equations for fat and ash. Publication year influenced the prediction of empty body water for both sets of equations and ash for one of the equations, whereas, breed type influenced the prediction of water, protein, and ash, but not fat for both equations. Overall, existing equations may have major limitations to predicting empty body protein and ash unless carcass protein and ash are known. Additionally, all the equations were affected by some combination of publication year, sex, and breed type for one or more chemical components. Thus, a more robust set of equations should be developed to account for sex, breed type, and more recent cattle genetics and management systems.

Effect of live yeast supplementation on energy partitioning and ruminal fermentation characteristics of steers fed a grower-type diet in heat-stress conditions

The objective of this trial was to determine the influence of live yeast supplementation (LY), environmental condition (ENV), and their interaction (TRT) on energy partitioning, nitrogen metabolism, and ruminal fermentation dynamics of steers receiving a grower-type diet. The effects of LY and ENV were investigated using a 2 × 2 crossover design that spanned five periods. Eight Angus-crossbred steers were randomly split into pairs and housed in four outdoor pens outfitted with an individualized feeding system. Animals were limit-fed a grower diet (DIET) at 1.2% shrunk body weight (SBW) with no live yeast supplementation (NOY) or a grower diet top-dressed with 10 g LY/d for 14 d (1.2 × 1012 CFU/d). On days 13 and 14, animals were subjected to one of two ENV conditions, thermoneutral (TN; 18.4 ± 1.1 °C, 57.6 ± 2.8% relative humidity [RH]) or heat stress (HS; 33.8 ± 0.6 °C, 55.7 ± 2.7% RH), in two side-by-side, single-stall open-circuit, indirect respiration calorimetry chambers. Data were analyzed using a random coefficients model. Carryover effects were examined and removed from the model if not significant. Gross (GE), digestible, metabolizable, heat, and retained energies were not influenced by DIET, ENV, or TRT (P ≥ 0.202). Gaseous energy, as a percentage of GE, tended to increase during HS (P = 0.097). The only carryover effect in the study was for oxygen consumption (P = 0.031), which could be attributed to the tendency of NOY (P = 0.068) to have greater oxygen consumption. DIET, ENV, or TRT (P ≥ 0.154) had no effects on total animal methane or carbon dioxide emissions. Similarly, DIET, ENV, or TRT (P ≥ 0.157) did not affect ruminal pH, redox, protozoa enumeration, ruminal ammonia concentrations, and acetate-to-propionate ratio. Propionate concentrations were the greatest in animals in TN conditions receiving LY (P = 0.034) compared to the other TRT. This effect is mirrored by TN-LY tending to have greater acetate concentrations (P = 0.076) and total VFA concentrations (P = 0.065). Butyrate concentrations tended to be greater for animals fed LY (P = 0.09). There was a tendency for LY to have elevated numbers of Fusobacterium necrophorum (P = 0.053). Although this study lacked effects of LY on energy partitioning, nitrogen metabolism, and some ruminal parameters during HS, further research should be completed to understand if LY is a plausible mitigation technique to enhance beef animals' performance in tropical and sub-tropical regions of the world.

Fat Deposition and Fat Effects on Meat Quality—A Review

Simple Summary

Animal fat deposition has a major impact on the meat yield from individual carcasses as well the perceived eating quality for consumers. Understanding the impact of livestock production practices on fat deposition and the molecular mechanisms activated will lead to a better understanding of finishing livestock. This enhanced understanding will also lead to the increased efficiency and improved sustainability of practices for livestock production. The impact of fat storage on physiological functions and health are also important. This review brings together both the production practices and the current understanding of molecular processes associated with fat deposition.

Abstract

Growth is frequently described as weight gain over time. Researchers have used this information in equations to predict carcass composition and estimate fat deposition. Diet, species, breed, and gender all influence fat deposition. Alterations in diets result in changes in fat deposition as well as the fatty acid profile of meat. Additionally, the amount and composition of the fat can affect lipid stability and flavor development upon cooking. Fat functions not only as a storage of energy and contributor of flavor compounds, but also participates in signaling that affects many aspects of the physiological functions of the animal. Transcription factors that are upregulated in response to excess energy to be stored are an important avenue of research to improve the understanding of fat deposition and thus, the efficiency of production. Additionally, further study of the inflammation associated with increased fat depots may lead to a better understanding of finishing animals, production efficiency, and overall health.

Effects of Protein Restriction and Subsequent Realimentation on Body Composition, Gut Microbiota and Metabolite Profiles in Weaned Piglets

Simple Summary

Protein restriction strategies are often used in weaned piglets to reduce the incidence of intestinal disorders that are sensitive to dietary protein supply, but may lead to a decline in production performance. Subsequent protein realimentation can alleviate the detrimental effects of reduced dietary protein on growth. However, the effects of protein realimentation on the body composition, gut microbiota and metabolite profiles of piglets are poorly understood. The present study, combining comparative slaughter methods, microbiome and metabolome analyses, demonstrated that protein restriction and subsequent realimentation lead to compensatory growth and compensatory protein deposition in piglets, and contribute to animal intestinal health by altering the gut microbiota and metabolite profiles.

Abstract

The objective of this study was to evaluate the effects of protein restriction and subsequent protein realimentation on the body composition, gut microbiota and metabolite profiles of piglets. Fifty weaned piglets were randomly assigned to two treatments: a normal protein (NP) group (20% crude protein (CP)) or a low protein (LP) group (16% CP) with five animals per pen and five pens per group. Treatment diets were fed for 14 d during the protein restriction phase, and then all pigs were fed the same nursery diets with a normal CP level (19% CP) during the protein realimentation phase until they reached an average target body weight (BW) of 25 ± 0.15 kg. At day 14 and the end of the experiment, one piglet close to the average BW of each pen was slaughtered to determine body composition, microbial composition and microbial metabolites. Results showed that there was no difference (p > 0.05) in the experimental days to reach target BW between the LP and NP groups. The average daily gain (ADG) and gain:feed ratio (G:F) during the protein restriction phase as well as BW at day 14, were significantly decreased (p < 0.05) in the LP group compared with the NP group. However, there were no significant differences (p > 0.05) during the protein realimentation phase and the overall experiment. Similarly, piglets in the LP group showed a significantly decreased body protein content (p < 0.05) at day 14, but not (p > 0.05) at the end of the experiment. The relative abundance of Parabacteroides, Butyricicoccus, Olsenella, Succinivibrio and Pseudoramibacter were significantly increased (p < 0.05), while the relative abundance of Alloprevotella and Faecalicoccus were significantly decreased (p < 0.05) in the LP group at day 14. At the end of the experiment, the piglets in the LP group showed a higher (p < 0.05) colonic relative abundances of Parabacteroides, unidentified Christensenellaceae and Caproiciproducens, and a lower (p < 0.05) relative abundance of unidentified Prevotellaceae, Haemophilus, Marvinbryantia, Faecalibaculum, Neisseria and Dubosiella than those in the NP group. Metabolomics analyses indicated that tryptophan metabolism and vitamin metabolism were enriched in the LP group at day 14, and glycerophospholipid metabolism and fatty acid esters of hydroxy fatty acid metabolism were enriched at the end of the experiment. Moreover, Spearman’s correlation analysis demonstrated that the microbial composition was highly correlated with changes in colonic metabolites. Collectively, these results indicated that protein restriction and subsequent realimentation lead to compensatory growth and compensatory protein deposition in piglets and contribute to animal intestinal health by altering the gut microbiota and its metabolites.

Effect of a high crude protein content diet during energy restriction and re-alimentation on animal performance, skeletal growth and metabolism of bone tissue in two genotypes of cattle

The objective of this study was to investigate the effect of diet crude protein (CP) content and metabolisable energy (ME) intake on skeletal growth and associated parameters of growing steers prior to and during compensatory growth in weight and catch-up growth in skeletal elongation. The experiment was a factorial design with two cattle genotypes [Brahman crossbred (BX, 178 ± 6 kg) and Holstein-Friesian (HF, 230 ± 34 kg)] and three nutritional treatments; high CP content and high ME intake (HCP-HME), high CP content and low ME intake (HCP-LME) and low CP content and low ME intake (LCP-LME) with the ME intake of HCP-LME matched to that of LCP-LME. Nutritional treatments were imposed over a 103 d period (Phase 1), and after this, all steers were offered ad libitum access to the HCP-HME nutritional treatment for 100 d (Phase 2). Steers fed the high CP content treatment with a low ME intake, showed higher hip height gain (P = 0.04), larger terminal hypertrophic chondrocytes (P = 0.02) and a higher concentration of total triiodothyronine in plasma (P = 0.01) than steers with the same ME intake of the low CP content treatment. In addition, the low CP treatment resulted in significant decreases in bone volume (P = 0.03), bone surface area (P = 0.03) and the concentration of bone-specific alkaline phosphatase in plasma (P < 0.001) compared to steers fed the HCP-HME treatment. A significant interaction between genotype and nutritional treatment existed for the concentration of thyroxine (T4) in plasma where HF steers fed LCP-LME had a lower T4 concentration in plasma (P = 0.05) than BX steers. All steers with a restricted ME intake during Phase 1 demonstrated compensatory growth during Phase 2. However, HF steers fed the LCP treatment during Phase 1 showed a tendency (P = 0.07) for a greater LWG during Phase 2 without any increase in dry matter intake. Results observed at the growth plate and hip height growth suggest that catch-up growth in cattle may also be explained by the growth plate senescence hypothesis. Contrary to our initial hypothesis, the results demonstrate that greater CP intake during ME restriction does not increase compensatory gain in cattle during re-alimentation.

Meat fatty acid and purine derivatives in hair lambs in tropical climates

An experiment was conducted to evaluate the effects of feed restriction and sex class on the intake and digestibility of nutrients as well as meat fatty acid profiles in Santa Ines lambs. Thirty lambs with initial body weights of 13 ± 1.49 kg and ages of 60 d were used in a completely randomized study with a 3 × 2 factorial arrangement consisting of three feeding levels (0 or ad libitum, 30%, and 60% feed restriction) and two sex classes (15 intact male and 15 castrated male), comprising five animals in each treatment. The experimental trial lasted 100 d. Increased feed restriction levels resulted in lower intake (P < 0.001) and higher digestibility of nutrients. There were decreases (P < 0.05) in the excretion of nitrogen compounds and purine derivatives when feed restriction increased. The feed restriction decreased (P < 0.05) the concentrations of C18:2n6 and C18:3n3 in the meat but did not affect the C18:2c9t11. The ratio of polyunsaturated fatty acids:monounsaturated fatty acid was higher in the 60% feed restriction. The results suggest that feed restriction improves nutrient utilization efficiency. The feed restriction up to 30% leads to a higher concentration of saturated fatty acids in meats.

Live growth performance, carcass grading characteristics, and harvest yields of beef steers supplemented zilpaterol hydrochloride and offered ad libitum or maintenance energy intake

A trial was conducted to examine live growth efficiency, harvest yields, and carcass grading performance of steers fed at maintenance (M) or at ad libitum (A) level of intake during zilpaterol hydrochloride (Z) supplementation. Single-sired, beef steers (n = 56; start of trial BW 590 ± 36 kg) blocked (n = 2) by weight and terminal implant were sorted into pairs (n = 14 per block) by weight. Pairs of steers were initially assigned to 0, 28, or 56 d of feeding. Within 28 or 56 d, pairs were assigned to M or A intake. Steers within a pair assigned to 56 d of feeding were randomly assigned to either 20 d of Z supplementation (90 mg/d per steer) with a 4 d withdrawal period prior to slaughter or to no ZH supplementation (C). Steers were housed and fed in individual pens. Weights of all non-carcass and carcass components were recorded at slaughter; carcasses were graded 24-h postmortem. Data were analyzed via a mixed model; the fixed effect was treatment combination with random effects of block and pair. Live growth data used harvest day as the repeated measure and animal as the subject. Single df contrasts were constructed for day 0 vs. day 28, day 0 vs. day 56, day 28 vs. day 56, M vs. A, and C vs. Z. Treatment impacted (P ≤ 0.05) live ADG; contrasts indicated A (1.33) was greater than M (0.14 kg), and Z (1.12) was greater than C (0.82 kg). Similarly, carcass ADG differences (P < 0.01) indicated A (1.04) was greater than M (0.36 kg), and Z (1.35) was greater than C (0.71 kg). Intake level altered BW and empty body weight (EBW); M cattle had reduced BW and EBW (P < 0.01, 585 and 540 kg) than A cattle (647 and 597 kg). Cattle fed at M had less carcass and internal cavity mass (P < 0.01, 359 and 79.4 kg) than A cattle (394 and 93.5 kg). Liver mass was reduced by M feeding (P < 0.01; M-5.03, A-6.69 kg) and Z treatment (P < 0.01; Z-5.64, C-6.06 kg). Moreover, mass of total splanchnic tissue was less (P < 0.01) for M cattle than A cattle (59.8 vs. 72.5 kg). Dressed carcass yield was greater (P < 0.01) for Z than C cattle (63.5 vs. 61.6%). Cattle fed at M had less 12th rib s.c. fat, lower numerical U.S. yield grades (P < 0.01; M-1.71 cm and 3.3, A-2.46 cm and 4.3) and lower numerical Canadian yield grades (P < 0.01; 51.9 vs. 53.9% for M and A, respectively) than A cattle. Results indicate that energy intake level and Z supplementation influence live and carcass growth, carcass transfer, kill yields, and carcass characteristics across time.

Effects of feed intake restriction during late pregnancy on the function, anti-oxidation capability and acute phase protein synthesis of ovine liver

Objective

An experiment was conducted to investigate the effects of feed intake restriction during late pregnancy on the function, anti-oxidation capability and acute phase protein synthesis of ovine liver.

Methods

Eighteen time-mated ewes with singleton fetuses were allocated to three groups: restricted group 1 (RG1, 0.18 MJ ME/kg W^0.75 d, n = 6), restricted group 2 (RG2, 0.33 MJ ME/kg W^0.75 d), n = 6) and a control group (CG, ad libitum, 0.67 MJ ME/kg W^0.75 d, n = 6). The feed restriction period was from 90 days to 140 days of pregnancy.

Results

The ewe’s body weight, liver weights, water, and protein content of liver in the restricted groups were reduced compared with the CG group (p<0.05), but the liver fat contents in the RG1 group were higher than those of the CG group (p<0.05). The increased hepatic collagen fibers and reticular fibers were observed in the restricted groups with the reduction of energy intake. The concentrations of nonesterified free fatty acids in the RG1 and RG2 groups were higher than those of the CG group with the reduction of energy intake (p<0.05), but there were decreased concentrations of lipoprotein lipase and hepatic lipase in both restricted groups compared with the CG group (p<0.05). In addition, the increased concentrations of β-hydroxybutyric acid, triglycerides, malondialdehyde, total antioxidant capacity and activities of superoxide dismutase activity and catalase were found in the RG1 group, and the concentrations of cholinesterase in the RG1 group were reduced compared with the CG group (p<0.05). For the concentrations of acute phase proteins, the C-reactive protein (CRP) in the RG1 group were reduced compared with the CG group, but there were no differences in haptoglobin relative to the controls (p>0.05).

Conclusion

The fat accumulation, increased hepatic fibrosis, antioxidant imbalance and modified synthesis of acute phase proteins were induced in ewe’s liver by maternal malnutrition during late pregnancy, which were detrimental for liver function to accommodate pregnancy.

Milk replacer restriction during early life impairs the live body weight and progesterone patterns of ewe lambs during the replacement period

Nutritional programming caused by feed restriction during the early life may counteract the profitability of the dairy sheep farm. However, most studies have been focused exclusively on the prenatal period, and scarce information regarding the effect of milk replacer (MR) restriction on feed efficiency [residual feed intake (RFI)] and progesterone patterns of replacement ewe lambs is available. Therefore, in the present study 40 Assaf female newborn lambs were penned individually and assigned randomly to 1 of 2 treatment groups (n = 20 per treatment). The first group of lambs was fed MR ad libitum (ADLB), whereas the second one (restricted, RES) only received approximately 62.5% of the MR intake measured in the ADLB group. All the lambs were weighed twice a week until they were 35 d old. Then 8 lambs from each group were killed and a morphological study of the gut was performed. Moreover, a piece of liver was cut to measure fat content and oxidative status. The rest of the ewe lambs (24) were weaned and offered a total mixed ration ad libitum to calculate the RFI during the replacement phase. Plasma samples were collected when ewe lambs were 8 mo old to perform a nontargeted metabolomic analysis on a hybrid quadrupole-time-of-flight mass spectrometer coupled to an ultra-high-performance liquid chromatographic system. Progesterone was also measured weekly on serum samples by sequential competitive immunoassay until the end of the experiment (9.5 mo old). The results observed indicate that moderated MR restriction promoted differences in the morphology of the gut of the 35-d-old lambs, but not in the apparent digestibility or feed efficiency traits (RFI) during the replacement phase. However, there was a trend toward reduced live body weight of the RES ewe lambs when they were 9.5 mo old. Moreover, progesterone patterns revealed that only 1 RES versus 4 ADLB ewe lambs had ovulated for the first time at the end of the experiment. This evidence suggests the existence of long-term effects caused by early feed restriction with negative consequences on live body weight and reproductive traits of replacement ewe lambs.

Differential transcript abundance in adipose tissue of mature beef cows during feed restriction and realimentation

Feed costs account for over 70% of the annual expenditures in cow/calf production. During the production year the cow uses nutrients to support conceptus growth, milk production, work (grazing and locomotion), and maintenance requirements. The majority of the nutrients are used to support maintenance. Substrate cycling has been identified as one of the major contributors toward energy expenditure associated with maintenance in mature cows. The objective of this study was to determine whether beef cows that differ in the efficiency of weight gain differ in the relative abundance of transcripts for metabolic regulation in adipose tissue. Mature beef cows were subjected to feed restriction followed by ad libitum feed. Adipose tissue from twelve cows with high (n = 6) and low (n = 6) gain based on growth performance during the ad libitum feeding period was evaluated for transcriptome expression differences. A total of 496 genes were differentially expressed and passed Bonferroni correction for the animals with greater gain between restriction and realimentation and 491 genes were differentially expressed among animals with lesser gains between feed restriction and realimentation. Of these two differentially expressed gene lists, 144 genes were common between animals with greater and those with lesser gain. Enriched biological processes included the TCA cycle, oxidative phosphorylation, respiratory electron transport chain and fatty acid metabolic processes. Specific to adipose tissue of low gaining animals was glycolysis and to high gain animals was coenzyme, steroid, cellular amino acid, nitrogen compound metabolic processes, and sensory perception. The oxidative phosphorylation, mitochondrial dysfunction and cholesterol biosynthesis pathways were commonly associated with the high gain animals between feed restriction and realimentation, as well as with the low gaining animals between the two time points. Unique to the high gaining animals were valine degradation and LPS/IL-1 mediated inhibition of RXR function pathways. In this discovery study, genes involved in lipid metabolism, mitochondrial respiration and oxidative phosphorylation pathways appear to be critical to mature cows during times of abundant feed after feed restriction.

Supplementation of metabolizable protein during late gestation and fetal number impact ewe organ mass, maternal serum hormone and metabolite concentrations, and conceptus measurements

To examine the effects of maternal metabolizable protein (MP) supplementation during late gestation on serum hormone and metabolites and organ masses, multiparous ewes (n = 45) carrying singletons or twins were allotted randomly (within pregnancy group) to 1 of 3 treatments: 60% (MP60), 80% (MP80), or 100% (MP100) of MP requirements. Blood samples were drawn before the initiation of diets (day 100) and before slaughter (day 130) for chemistry panel analysis and weekly for hormone analysis including progesterone (P4) and estradiol-17β (E2). At day 130, ewe organ masses were recorded. Despite being fed isocaloric diets, MP60 ewes gained less weight throughout pregnancy compared with MP80 and MP100 ewes which were similar. Although diet did not impact E2 or P4 concentrations, ewes carrying twins had greater (P < 0.05) concentrations of both as gestation advanced. Albumin, aspartate aminotransferase, and total protein were reduced (P < 0.05) in MP60 compared with MP100 ewes near term. There was a diet by fetal number interaction (P = 0.03) for lactate dehydrogenase. Twin-carrying MP80 ewes had greater lactate dehydrogenase compared with all other groups on day 130 of gestation. Ewes that were fed MP80 had greater body weight on day 130 of gestation compared with MP60 ewes. Kidney and heart weights were lighter in MP60 ewes compared with MP80 ewes. There was a maternal diet by fetal number interaction (P = 0.05) on fetal weight per unit empty ewe body weight. In ewes carrying singletons, MP60 ewes supported less fetal weight compared with MP100. In contrast, MP60 ewes supported more fetal mass compared with MP100 ewes when carrying twins. The level of protein, and not just total energy, in the diet appears to impact some aspects of the maternal system. Moreover, it appears some measurements of mobilizing maternal body resources are enhanced in ewes carrying twins.

Variation in feed utilisation by sheep undergoing compensatory growth following underfeeding with and without additional dietary nitrogen in western China

Small mixed farming systems in developing economies often rely on compensatory growth to recover livestock weight lost during seasonal feed shortages; however, deficit feed management may continue to affect the capacity of livestock to efficiently use feeds even after adequate feeding has resumed. Accordingly, we compared the difference in liveweight gain and feed utilisation over time in Tan weaner sheep in western China, during a period of ad libitum compensatory feeding after alternative feed deficit scenarios. During the feed deficit period, sheep were offered, at 80% maintenance requirements, corn straw, corn grain and lucerne hay in a respective ratio of either 80 : 20 : 0 (S1 ration: metabolisable energy = 7 MJ/kg DM, crude protein = 40 g/kg DM) or 55 : 20 : 25 (S2 ration: metabolisable energy = 8 MJ/kg DM, crude protein = 65 g/kg DM) for 20 days. All sheep were then offered an ad libitum supply of the S2 ration for a further 20 days, during which DM digestibility (DMD), energy intake and liveweight was measured and compared at 5-day intervals. Results indicated that sheep previously fed the S1 ration were not able to digest as much of the ad libitum S2 ration as those previously fed the S2 ration, experiencing significantly lower DMD, energy intake and average daily weight gain. The difference in the effect of the two restrictive feeding treatments on the digestibility of the ad libitum S2 ration gradually decreased over time, indicative of a recovery adaptation during ad libitum feeding period. The rate of DMD recovery post-realimentation was greater in the S1 sheep, likely due to their significantly lower DMD values immediately following underfeeding. We concluded that the comparatively higher nutritive value of the S2 ration sustained rumen digestive function throughout the restrictive feeding period, permitting sheep to commence re-feeding under conditions that are more favourable. Additionally, it is evident that reliance on livestock winter rations typical in western China, as expressed by the S1 ration, degraded ruminant digestive conditions to such an extent that feed was used with reduced efficiency even after being supplied in adequate quantities.

Desenvolvimento dos órgãos e deposição de gorduras em cabritos Canindé sob restrição alimentar

RESUMO Objetivou-se avaliar o efeito da restrição alimentar sobre o desenvolvimento dos órgãos e deposição de gordura em caprinos Canindé castrados. Foram utilizados 21 cabritos confinados, em um delineamento inteiramente casualizado, com peso inicial de 15,9 ± 1,03kg. Os cabritos foram alocados em três níveis de restrição alimentar (sete animais por nível): ad libitum (alimentados à vontade); restrição moderada (restrição de 20% em relação à quantidade de matéria natural consumida pelos animais alimentados ad libitum) e restrição severa (restrição de 40% em relação à quantidade de ração consumida pelos animais alimentados ad libitum). A ração experimental apresentou uma proporção de 55% de volumoso (Tifton) e 45% de concentrado. Aos 110 dias de experimento os cabritos foram abatidos com peso médio de 23,5 kg ± 2,5 kg. Esvaziou-se o trato gastrointestinal (TGI), a bexiga e a vesícula biliar e foram mensurados os seus pesos para determinação do peso de corpo vazio (PCV). Foram separados e registrados os pesos dos órgãos (baço, coração, fígado, pâncreas, pulmões, rins, sangue, TGI) e dos depósitos de gordura (cardíaca, mesentérica, omental e pélvico-renal). A restrição alimentar em caprinos Canindé afetou o peso absoluto dos órgãos e das gorduras (P < 0.05) que estão mais envolvidas com a função de reserva energética (mesentérica, omental e pélvico-renal), no entanto, não afetou o percentual dos órgãos em relação ao PCV (P > 0.05), indicando que mesmo sob restrição o desenvolvimento dos órgãos é proporcional ao desenvolvimento do corpo.

Role of the Small Intestine in Developmental Programming: Impact of Maternal Nutrition on the Dam and Offspring

Small-intestinal growth and function are critical for optimal animal growth and health and play a major role in nutrient digestion and absorption, energy and nutrient expenditure, and immunological competence. During fetal and perinatal development, the small intestine is affected by the maternal environment and nutrient intake. In ruminants, altered small-intestinal mass, villi morphology, hypertrophy, hyperplasia, vascularity, and gene expression have been observed as a result of poor gestational nutrition or intrauterine growth restriction. Although many of these data come from fetal stages, data have also demonstrated that nutrition during mid- and late gestation affects lamb small-intestinal growth, vascularity, digestive enzyme activity, and gene expression at 20 and 180 d of age as well. The small intestine is known to be a highly plastic tissue, changing with nutrient intake and physiological state even in adulthood, and the maternal small intestine adapts to pregnancy and advancing gestation. In ruminants, the growth, vascularity, and gene expression of the maternal small intestine also adapt to the nutritional plane and specific nutrient intake such as high selenium during pregnancy. These changes likely alter both pre- and postnatal nutrient delivery to offspring. More research is necessary to better understand the role of the offspring and maternal small intestines in whole-animal responses to developmental programming, but programming of this plastic tissue seems to play a dynamic role in gestational nutrition impacts on the whole animal.

Effect of rate of body weight gain of steers during the stocker phase. II. Visceral organ mass and body composition of growing-finishing beef cattle

Two experiments were conducted to examine the effect of rate of BW gain during the stocker phase on visceral organ mass and body composition of growing-finishing cattle that had grazed dormant native range (DNR) or winter wheat pasture (WP). In each experiment, fall-weaned steers were allotted randomly to 1 of these stocker production programs: 1) control, 1.02 kg · steer(-1) · d(-1) of a 40% CP cottonseed meal-based supplement during grazing of DNR (CON); 2) corn/soybean meal-based supplement fed at 1% of BW during grazing of DNR (CORN); 3) grazing WP at a high stocking rate to achieve a reduced rate of BW gain (LGWP); and 4) grazing WP at a low stocking rate to achieve an increased rate of BW gain (HGWP). In Exp. 1, 3 steers per treatment were harvested after winter grazing (138 d). The remaining WP steers were transitioned into a finishing phase and DNR steers were allowed to graze the same pastures for another 115 d before entering a feedyard. In Exp. 2, steers grazed respective pastures until each treatment reached an estimated HCW of 200 kg (262, 180, 142, and 74 d, respectively, for CON, CORN, LGWP, and HGWP treatments), at which time 4 steers per treatment were randomly selected for intermediate harvest before finishing. At the end of the finishing period, 4 additional steers from each treatment were randomly selected for final carcass measurements. All steers were fed to a common 12th rib fat thickness of 1.27 cm. After winter grazing in Exp. 1, HGWP steers had the greatest (P < 0.01) mesenteric/omental fat, total viscera, total splanchnic tissue mass, and carcass and empty body fat, compared with the other treatments. In Exp. 2 at intermediate harvest, WP steers had greater (P < 0.03) mesenteric/omental fat, total viscera, and total splanchnic tissue mass, compared with CORN steers, with CON steers being intermediate. Also, the WP steers had greater (P < 0.02) carcass and empty body fat, compared with CORN steers, with CON steers being intermediate. At final harvest in Exp. 2, LGWP steers had the least total viscera and total splanchnic tissue mass, compared with the other treatments. However, there were no differences (P > 0.53) among treatments for carcass or empty body fat. Stocker systems using WP or DNR result in cattle with differences in body fat and visceral organ mass before finishing; this may influence feedlot efficiency, even though there were no differences in body fat and visceral organ mass at the end of the finishing period.

Effects of nutritional plane and selenium supply during gestation on visceral organ mass and indices of intestinal growth and vascularity in primiparous ewes at parturition and during early lactation

Objectives were to investigate effects of nutritional plane and Se supply during gestation on visceral organ mass and intestinal growth and vascularization in ewes at parturition and during early lactation. Primiparous Rambouillet ewes (n = 84) were allocated to 2 × 3 × 2 factorial arrangement of treatments. Factors included dietary Se [adequate Se (ASe, 11.5 μg/kg BW) or high Se (HSe, 77.0 μg/kg BW)], nutritional plane [60% (restricted; RES), 100% (control; CON), or 140% (high; HIH)], and physiological stage at necropsy (parturition or d 20 of lactation). At parturition, lambs were removed and 42 ewes (7 per treatment) were necropsied. Remaining ewes were transitioned to a common diet which met lactation requirements and mechanically milked for 20 d. In the absence of interactions (P > 0.10), main effects are reported. At parturition, stomach complex and liver masses were greatest for HIH, intermediate for CON, and least for RES (P < 0.02). Small intestinal mass was greater (P ≤ 0.002) for HIH than RES and CON, and greater (P < 0.01) for ASe than HSe. During early lactation, RES and CON gastrointestinal masses increased disproportionally to BW (P < 0.05). At parturition, jejunal mucosal density was less (P ≤ 0.01) for RES than CON and HIH, whereas CON had greater (P < 0.003) jejunal mucosal RNA concentration and RNA:DNA than RES and HIH. Although there were no differences (P > 0.17) at parturition, jejunal cell percent proliferation was greatest in RES, intermediate in CON, and least in HIH (P ≤ 0.09) at d 20 lactation. At both stages, RES had less (P = 0.01) jejunal capillary area density than HIH and less (P ≤ 0.03) capillary surface density than CON and HIH. During lactation, jejunal capillary size was greater (P = 0.04) for ewes previously fed HSe compared with ASe. At parturition, ASe-HIH had greater (P < 0.02) jejunal mucosal endothelial nitric oxide synthase 3 mRNA than all other treatments and greater (P = 0.10) vascular endothelial growth factor (VEGF) than all treatments, except ASe-RES. In addition, CON had less (P ≤ 0.08) jejunal VEGF receptor-1 (FLT1) mRNA compared with RES and HIH, and ASe had greater (P = 0.003) FLT1 than HSe at parturition. Ewes fed HIH had greater (P = 0.04) jejunal VEGF receptor-2 mRNA compared with RES. Results indicate that maternal intestinal growth and vascularization are responsive to nutritional plane and dietary Se during gestation and undergo changes postpartum when under similar lactational management.

Maintenance energy requirements of growing pigs and calves are influenced by feeding level

The conventional regression method for partitioning heat production (HP) in growing animals between HP associated with either maintenance or growth assumes maintenance HP to be independent of feeding level (FL). However, there are indications that this assumption is not correct and an alternative method is proposed in this study from a reanalysis of 3 trials. In trial 1, 73-, 152-, and 237-kg calves received one milk replacer at 77, 84, 92, and 100% of their ad libitum metabolizable energy (ME) intake. In trial 2, 70-kg barrows received one diet at 60, 80, and 100% of their ad libitum ME intake {2600 kJ ME/[kg body weight (BW)(0.60) · d]}. In trial 3, 60-kg barrows received a basal diet [1700 kJ ME/(kg BW(0.60) · d)] or 4 diets consisting of the basal diet plus 850 kJ ME/(kg BW(0.60)·d) of starch alone or starch with corn gluten, casein, or vegetable oil. In the 3 trials (n = 48, 18, and 28, respectively), HP and activity-related HP were measured on individuals pigs and calves in respiration chambers for 6 d (fed state) and fasting HP (FHP; at zero activity) was calculated as the asymptotic value of HP kinetics on d 7 (feed-deprived state). The FHP changed by 0.22 kJ in calves and 0.14 kJ in pigs/kJ ME intake change during the previous days. The efficiency of using ME for maintenance and growth [k(mg); 1- (HP - FHP)/ME] was not affected by FL (calves: 84%, pigs in trial 2: 74%). In trial 3, k(mg) varied between diets in connection with variations in efficiencies between nutrients (from 55% for corn gluten to 85% for lipid). This new method of representing partitioning of ME intake considers FHP as variable with FL, does not require estimates of maintenance ME requirements, includes efficiencies that depend on diet characteristics, and is not biased by metabolic adaptations of the animal to FL.

The effects of diet, slaughter weight and docking on growth, carcass composition and meat quality of fat-tailed Barbarine lambs. A review

This review summarises the main factors that influence meat production and quality in fat-tailed Barbarine (FTB) lambs. As a general feature, FTB lamb's growth is moderate, and the average daily gain ranges between 100 and 350 g. The carcass being relatively fatty, carcass fat content varies from 10% to 32%; white fat and rose meat are often dominant in these carcasses. The meat fatty acid profile of this fat-tailed breed is similar to that of thin-tailed ones, with a prevalence of palmitic, stearic and oleic acids. The order of dissected adipose tissues accumulation, estimated by allometry coefficients, is in agreement with observations in thin-tailed sheep. However, tail fat allometry coefficient is closer to kidney fat values rather than to the subcutaneous one. Concerning effects of feed level, growth of FTB lambs fed silage is higher than those fed oat hay. With moderate concentrate supply, FTB lambs' growth is more pronounced on pasture diet than on the feedlot (FL) diet. Furthermore, at similar slaughter weights, carcasses of lambs fed pasture diet have less tail and carcass fat than those from lambs fed FL diet (5% and 18% vs. 9% and 24% for grazing and FL lambs, respectively). No difference in fat colour, fat firmness or cooked meat flavour is observed between carcasses obtained at different slaughtering weight (i.e. from 25 to 35 kg). The tail docking of FTB improved lambs' growth particularly before weaning. Its effect on carcass composition and fat proportion depends on stage of slaughtering and type of fattening diet. For suckled lambs (4 months), the docking resulted in the lower carcass fat weight (and proportion), while for fattened lambs, carcass composition was similar for all types of lambs. Overall, FTB lambs always grow slower than Noire de Thibar lambs. This is particularly pronounced during the fattening phase. Then, for FTB breed, the possibilities to obtain heavy carcasses are at risks of fat accumulation, 22.8% vs. 14.4% for FTB and Noire de Thibar thin-tailed lambs, respectively. However, the main advantage of FTB breed is that adults are well adapted to food scarcity and may produce lambs even under harsh conditions.

The effect of nutrition during early life on voluntary food intake by lambs between weaning and 2 years of age

Two experiments were carried out with Scottish Blackface lambs to investigate the effects of restricted nutrition during pregnancy and lactation on voluntary food intakes (VFI) between weaning and 2 years of age. Ewes were given diets providing 0·7 (LP) or 10 (HP) of their estimated metabolizable energy requirements during the last 6 weeks of pregnancy and subsequently grazed swards with mean sward surface heights of approximately 3 cm (LL) or 6 cm (HL) during lactation. All lambs were weaned at 17 weeks of age. In experiment 1, four treatment combinations (LP-LL, LP-HL, HP-LL and HP-HL) were applied and female lambs were studied. In experiment 2, two treatment combinations (LP-LL and HP-HL) were applied and male lambs were studied. In both experiments the lambs received a common level of nutrition between weaning and 2 years of age.

In both experiments, mean live weights were proportionately 0·2 higher for HP-HL than for LP-LL lambs at weaning (P < 0·001) and in experiment 2 mean live weights and body condition scores were still higher in HP-HL than in LP-LL lambs at 2 years of age (P < 0·05). Abomasum weights were higher in HP than in LP lambs at birth and higher in HP-HL than in LP-LL lambs at weaning in experiment 1 and the weights of the rumen and dimensions of the rumen villi were greater in HP-HL than in LP-LL lambs at weaning in both experiments (P < 0·05). The treatments had no effect on lipid content or mean adipocyte diameter in the main fat depots at birth or weaning. There were no treatment effects on VFI in either experiment. It was concluded that restricted nutrition during late pregnancy and early lactation does not affect VFI between weaning and 2 years of age in sheep, even though there are differences in live weight and the development of the gastrointestinal tract at weaning and there may be long-term effects on live weight and body condition, particularly in male animals.

Effect of intake level during milk-feeding period and protein content in the post-weaning diet on performance and body composition in growing lambs

The effect of intake level during the milk-feeding period and dietary protein content during the post-weaning period on performance, weight of components of the digestive tract and carcass and non-carcass chemical composition was investigated in 28 Churra lambs. A 2 × 2 factorial design was used with two intake levels during the milk-feeding period (Lmilk: 0·9 and Hmilk: 1·5 MJ gross energy per kg M0·75daily) and two concentrate supplements (Lprotein:barley grain and Hprotein: barley grain plus 200 g/kg fish meal) during the post-weaningperiod. After selecting an initial slaughter group of four 2-day-old lambs, 12 lambs were assigned randomly to each of two intake levels during a 4-week milk-feeding period and given food individually. Four lambs from each intake level were slaughtered at weaning (30 days old) and the remaining 16 were weaned between 30 and 49 days old (weaning period). Eight lambs from each nutritional regimen during the milk-feeding period were further divided into two equal groups and given food individuallyad libitumwith hay and the post-weaning concentrate, according to the experimental design until thefinal slaughter weight (20 kg) (post-weaning period). Lmitk lambs showed a capacity to grow as well as the Hmilkduring the weaning and post-weaning period and there were no differences (P> 0·05) in dry-matter intake and food conversion ratio among treatments. Before weaning, the weight of the reticulo-rumen was not affected by the intake level during the milk-feeding period. The most affected component of the gastrointestinal tract was the small intestine as proportion of the digestive tract which was lower in Lmilklambs (P< 0·05). At 20 kg live weight, the relative size of the reticulo-rumen was greater (P< 0·01) and the abomasum (P< 0·05) and large intestine (P< 0·01) were smaller in lambs which were given the Hprotein concentrate after weaning. The organic matter apparent digestibility (OMD,P< 0·05) and crude protein apparent digestibility (CPD,P< 0·05) of the post-weaning diets was greater in Lmilklambs and the Hproteinpost-weaning diet was associated with a greater dry-matter apparent digestibility, OMD and CPD when lambs were close to final slaughter weight. At 20 kg live weight, the proportion of protein in the carcass of Lmilklambs was greater (P< 0·05) than in Hmilklambs. The greater growth of the reticulo-rumen of the Lmilklambs might have increased solid food intake after the milk-feeding period, led to greater CPD of post-weaning diets and had consequences in terms of carcass composition.

Effects of winter growing program on visceral organ mass, composition, and oxygen consumption of beef steers during growing and finishing

The purpose of this experiment was to investigate the effects of winter growing program on organ mass, composition, and oxygen consumption in beef steers. A total of 46 steers were used for the experiment. Four steers were randomly selected as an initial slaughter group. Remaining steers were randomly allotted to 1 of 4 treatment groups: 1) fed a high-concentrate diet for ad libitum intake (CF); 2) grazed on wheat pasture (WP); 3) fed a sorghum silage-based growing diet (SF); or 4) program fed a high-concentrate diet (PF). Steers in the WP, SF, and PF groups were managed to achieve approximately equal rates of BW gain during the growing phase. After the growing phase (112 d), steers in the WP, SF, and PF treatments were adapted to a high-concentrate diet for finishing. Steers from all treatments were slaughtered at a fat thickness of 1.27 cm as estimated by ultrasound. In addition, 6 steers from each treatment were randomly selected for slaughter at the end of the growing phase. Weights of all individual organs were measured and tissue samples of duodenum and liver collected. At the end of the growing phase, WP steers had greater (P < 0.05) small intestine, liver, and kidney mass than SF and PF steers. In contrast, mesenteric fat mass and total visceral fat content were greatest (P < 0.01) for PF, intermediate for SF, and least for WP steers. Mass of total viscera and total splanchnic tissues (TST) did not differ (P > 0.10) among treatments. At final slaughter, mass of mesenteric fat, total viscera, and TST were similar among treatments, but liver weights remained greatest (g/kg of empty BW; P < 0.01) for WP steers. There were no differences in oxygen consumption of duodenum or liver tissue on an equal weight basis (microL.min(-1.)g(-1)) at the end of either period. Growing program affected mass of components of the TST at the end of the growing phase, which contributed to differences in rate of splanchnic organ growth during finishing. We conclude that program feeding a high-concentrate diet during the growing phase may result in greater ADG and G:F during the subsequent finishing period compared with forage-based diets due to less accretion of visceral organ mass resulting in reduced maintenance energy requirements during finishing.

Supplementations of Hyparrhenia rufa -dominated hay with groundnut cake- wheat bran mix: effects on feed intake, digestibility and nitrogen balance of Somali goats

A digestibility and nitrogen (N) balance experiment was conducted using twenty yearling male Somali goats weighing 23.4 +/- 2.02 (mean+/-SD). The objectives of the study were to evaluate the effects of supplementation with graded levels of mixture of groundnut cake and wheat bran at a ratio of 3:1 on DM basis on feed intake, apparent digestibility and N balance in Somali goats. The experimental design was a completely randomized design consisting of five animals in each treatment. The dietary treatments included ad libitum feeding of hay (T1, control), and daily supplementation with 200 (T2, low) 300 (T3, medium) and 400 g DM (T4, high) of the concentrate mix. Increased level of supplementation reduced (P < 0.001) daily hay DM intake. Digestibility of crude protein (CP) was higher (P < 0.001) for the supplemented goats. Urinary nitrogen, total nitrogen excretion and retention increased (P < 0.01) with the level of supplementation. It was concluded that supplementation with groundnut -wheat bran mixture promoted feed intake and digestibility of DM, CP, and N retention in Somali goats fed hay. However, supplementation at the medium level appeared to be more effective since it promoted similar N balance with the high level of supplementation.

Effects of restricted feeding and re-feeding of Barbarine lambs: intake, growth and non-carcass components

Abstract Fifty intact male Barbarine lambs were used to assess the effects of restricted feeding and re-alimentation on intake, growth and non-carcass components. Five lambs were slaughtered at the start of the trial, the remainder were randomly allocated into three groups. One group was offered only stubble grazing (low: L), another, also on stubble, received, indoors, an average of 80 g dry matter (DM) of soya-bean meal per day (medium: M); the third group was kept indoors and had free access to hay and 450 g of concentrate per day (high: H). At the end of this restriction period (70 days), five lambs per group were slaughtered. The 10 remaining animals in each group were divided into two groups receiving concentrate and hayad libitum. The crude protein content (CP) of the concentrate was 160 and 210 g/kg DM for the two treatments, respectively. At the end of the trial all animals were slaughtered at 37·61 ± 2·05 kg live weight.

In the restriction period, sheep from the H group had a significantly higher growth rate (108 g/day) than L group (61 g/day) with M intermediate. The empty body weight (EBW) as well as carcass weight were significantly higher in H than in restricted sheep. Digestive tract components and liver weight were the same for all treatments. However, skin weight was significantly (P< 0·01) affected by dietary treatment. The heart and lungs were also heavier in H lambs than in the two other groups. Conversely, the relative weights of gut and liver as proportion of EBW increased in restricted lambs, while that of skin and red organs was not affected by diet.

In the re-alimentation period and with both CP levels, the compensating animals showed the same growth rate as the previous unrestricted ones. At the end of this period, organ weights, in both absolute and relative value, were comparable among lambs of the three nutritional histories and two CP level. The absolute and proportional daily gains were similar in all animals for visceral and external organs, but they were significantly higher in H lambs than in L and M ones for the omental and mesenteric fat and testis.

Energy expenditure and restriction of energy intake: could energy restriction alter energy expenditure in companion animals?

The treatment of obesity in companion animals frequently focuses on restriction of energy intake. One important question with this treatment is whether dietary energy restriction (ER) produces a sustained decrease in mass-adjusted energy expenditure (EE), which prevents further weight loss and promotes rapid regain of body weight during lapses in dietary ER. This review summarizes studies that investigated the effects of dietary ER on EE at the whole-animal, organ, and cellular level. Whole-animal studies indicate that long-term dietary ER either decreases or does not affect mass-adjusted EE. The reason for this discrepancy between studies is not entirely clear, although analysis of data pooled from multiple studies suggests that a reduction in mass-adjusted EE with long-term ER would be observed if the sample size were sufficiently large and appropriate methods were used to adjust EE for body size. At the organ level, attempts were made to determine whether alterations in organ mass can entirely explain changes in EE with dietary ER. However, these studies were not conclusive, and it remains to be determined whether changes in EE exceed those that would be predicted from ER-induced alterations in organ mass. At the cellular level, there is evidence that dietary ER may induce sustained decreases in substrate oxidation, mitochondrial proton, and Na+-K+-ATPase activity in at least some tissues. These results are consistent with the idea that dietary ER may induce decreases in cellular EE. However, future studies integrating measurements at the whole-animal, organ, and cellular level will be required to determine definitively whether dietary ER produces sustained decreases in tissue or cellular EE.

The effect of spineless cactus (Opuntia ficus-indica f. inermis) supplementation on growth, carcass, meat quality and fatty acid composition of male goat kids

The objective of this study was to determine the effects of grain compared to spineless cactus feeding on goat kids growth, carcass characteristics and FA profile. For this purpose, 21 kids were used and allocated to 3 groups receiving a low quantity (200g) of oat hay. The control group received ad libitum a concentrate containing 130g crude protein (CP) per kg of dry matter (C130). The second group received half of that contained consumed by the control one but its CP content was 260g/kg DM and spineless cactus ad libitum (C260-Cac). In the third group, concentrate intake was limited to soya bean at a quantity that provided the same CP quantity as the two other groups and also cached spineless cactus was distributed ad libitum (Soya-Cac). Animals of all groups had free access to water. At the end of the growth trial which lasted for 74 days, all kids were slaughtered. Samples of longissimus dorsi muscle were used for meat quality and FA composition study. Animals in the control group and those in the C260-Cac had higher growth rate than Soya-Cac diet animals. Muscle and adipose tissue mean weights were higher in the first groups while the bone weight was similar in all treatments. Animals given Soya-Cac diet had relatively less fat (10.5%) than those fed other diets (p<0.001). Carcass fat content tended to be lower (p=0.07) in C260-Cac goats (13.5%) than in those of the C130 group (15.8%). The ultimate pH ranged between 6.18 and 6.48; it was higher in meat from control goats (C130) than in animals receiving cactus. Dietary treatment had no significant effect (p>0.05) on meat moisture, ash, crude fat and protein contents. The intra muscular lipid composition in fatty acids showed differences between the control group and those receiving cactus. Cactus in the diet was associated with more C18:2 and conjugated linoleic acid (CLA) as well as a higher proportion of PUFA and PUFA:SFA ratio than control ones. In conclusion, this study showed that cactus feeding of goat kids maximises the proportion of CLA, PUFA and PUFA:SFA ratio.

Effect of live weight gain of steers during winter grazing: III. Blood metabolites and hormones during feedlot finishing12

Two experiments were conducted using 48 Angus x Angus-Hereford steers in each experiment to determine the effect of previous winter grazing BW gain on jugular concentrations of metabolites and hormones during feedlot finishing. In each experiment, steers were randomly assigned to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) with 0.91 kg/d of a 41% CP (DM basis) supplement. Steers grazed for 120 or 144 d in Exp. 1 and 2, respectively. Plasma and serum were collected from all steers before placement into a feedlot, and six or seven times during finishing in Exp. 1 and 2, respectively. In Exp. 1, before steers entered the feedlot, concentrations of insulin, triiodothyronine (T3), and thyroxine (T4) were greater (P < 0.05) in HGW than in LGW or NR steers, and concentrations of IGF-I and plasma urea-N were greater (P < 0.05) in steers that grazed wheat pasture than in NR steers. In Exp. 2, concentrations of glucose, T3, T4, and IGF-I were greater (P < 0.05) in steers that grazed wheat pasture than NR steers. In Exp. 1 (P < 0.19) and 2 (P < 0.86), glucose concentration did not differ among treatments during finishing. In Exp. 1, insulin concentration across days on feed was greater for HGW than LGW steers, which were greater than for NR steers (treatment x day interaction, P < 0.03). In Exp. 2, insulin concentration increased (P < 0.001) as days on feed increased. Concentrations of IGF-I were greater in steers that had grazed wheat pasture, whereas the increase in IGF-I with increasing days on feed was greater for NR steers (treatment x day interaction, P < 0.003). Concentrations of T3 and T4 during finishing were greater (P < 0.001) in HGW and LGW than in NR steers in Exp. 1. In Exp. 2, T4 concentration also differed (P < 0.009) among treatments (HGW > LGW > NR). In Exp. 2, final concentration of glucose was greater (P < 0.01) in NR than in HGW and LGW steers, and serum insulin concentration was greater (P < 0.04) in NR than LGW steers. Final concentrations of T3 (P < 0.01) and T4 (P < 0.004) were greater in NR than in HGW steers. Our data show that previous BW gain can affect blood metabolites and hormones in steers entering the feedlot. However, lower concentrations of T3, T4, and IGF-I in steers when they entered the feedlot did not inhibit the growth response of previously restricted steers.

Effect of live weight gain of steers during winter grazing: I. Feedlot performance, carcass characteristics, and body composition of beef steers1,2,3

Two experiments were conducted to examine the effect of previous BW gain during winter grazing on subsequent growth, carcass characteristics, and change in body composition during the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range (NR) supplemented with 0.91 kg/d of cottonseed meal. Winter grazing ADG (kg/d) for HGW, LGW, and NR steers were, respectively, 1.31, 0.54, 0.16 (Exp. 1) and 1.10, 0.68, 0.15 (Exp. 2). At the end of winter grazing, four steers were selected randomly from each treatment to measure initial carcass characteristics and chemical composition of carcass, offal, and empty body. All remaining steers were fed a high-concentrate diet to a common backfat end point. Six steers were selected randomly from each treatment for final chemical composition, and carcass characteristics were measured on all steers. Initial fat mass and proportion in carcass, offal, and empty body were greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both experiments. Live BW ADG and gain efficiency during the finishing phase did not differ (P = 0.24) among treatments, but DMI (% of mean BW) for NR and LGW was greater (P < 0.003) than for HGW steers. Final empty-body composition did not differ (P = 0.25) among treatments in Exp. 1. In Exp. 2, final carcass and empty-body fat proportion (g/kg) was greater (P < 0.03) for LGW and NR than for HGW steers. Accretion of carcass fat-free organic matter was greater (P < 0.004) for LGW than for HGW and NR steers in Exp. 1, but did not differ (P = 0.22) among treatments in Exp. 2. Fat accretion in carcass, offal, and empty body did not differ (P = 0.19) among treatments in Exp. 1, but was greater (P < 0.05) for LGW and NR than for HGW steers in Exp. 2. Heat production by NR steers during finishing was greater (P < 0.02) than by HGW steers in Exp. 1 and 2. Differences in ADG during winter grazing and initial body fat content did not affect rate of live BW gain or gain efficiency during finishing. Feeding steers to a common backfat thickness end point mitigated initial differences in carcass and empty-body fat content. However, maintenance energy requirements during finishing were increased for nutritionally restricted steers that were wintered on dormant native range.

Effect of live weight gain of steers during winter grazing: II. Visceral organ mass, cellularity, and oxygen consumption1,2

Two experiments were conducted to examine the effect of BW gain during winter grazing on mass, cellularity, and oxygen consumption of splanchnic tissues before and after the feedlot finishing phase. In each experiment, 48 fall-weaned Angus x Angus-Hereford steer calves were assigned randomly to one of three treatments: 1) high rate of BW gain grazing winter wheat (HGW), 2) low rate of BW gain grazing winter wheat (LGW), or 3) grazing dormant tallgrass native range supplemented with 0.91 kg/d of a 41% CP supplement (NR). At the end of winter grazing, four steers were selected randomly from each treatment for initial slaughter to measure organ mass, cellularity, and oxygen consumption. All remaining steers were placed into a feedlot and fed to the same backfat end point (1.27 cm). Six steers were selected randomly from each treatment for final organ mass, cellularity, and oxygen consumption. Initial empty BW (EBW) was greatest (P < 0.001) for HGW, intermediate for LGW, and least for NR steers in both Exp. 1 and 2 (355 > 263 > 207 +/- 6.5 kg and 337 > 274 > 205 +/- 8.7 kg, respectively). For both experiments, the initial total gastrointestinal tract (GIT; g/kg of EBW) proportional weight was greater (P < 0.05) in NR steers than in LGW, and LGW steers had greater (P < 0.05) initial GIT proportional weight than HGW steers. Proportional weight of total splanchnic tissues (TST; g/kg of EBW) did not differ (P < 0.19) among treatments. Initial duodenal RNA concentration and RNA:protein were greater (P < 0.02) in LGW than in HGW steers, and NR steers were intermediate. Initial in vitro liver O2 consumption was greater (P < 0.09) in HGW and LGW than in NR steers (34.5 > 16.9 mL/min), whereas initial small intestinal oxygen consumption was greater (P < 0.01) in LGW than in HGW and NR steers (12.1 > 5.2 mL/min). Ruminal papillae oxygen consumption did not differ (P < 0.55) among treatments. The rate of decrease of GIT (g x g EBW(-1) x d(-1)) during finishing was greater in NR than in HGW and LGW steers in both Exp. 1 and 2, but mesenteric fat (g x g EBW(-1) x d(-1)) increased for NR steers, resulting in a similar (P < 0.75) increase in TST across the finishing period for all treatments. Similar rates of increase in TST across the finishing phase corresponded with similar rates of live and carcass weight gain among treatments. Our data support the hypothesis that increased visceral organ mass increases maintenance energy requirements of growing cattle.

Effect of the live weight gain of steers during winter grazing on digestibility, acid-base balance, blood flow, and oxygen consumption by splanchnic tissues during adaptation and subsequent feeding of a high-grain diet1,2

Ten multicatherized steers were used in a completely random design to determine the effect of previous BW gain on blood flow, acid-base balance, and oxygen consumption across portal-drained viscera and liver of growing beef steers fed a high-grain diet. Treatments were high (1.31 +/- 0.09 kg/d) or low (0.68 +/- 0.07 kg/d) daily BW gain during an 82-d winter wheat pasture grazing period and a subsequent 37-d transition period. Blood flow, blood gas measurements, and oxygen consumption were determined on d 0, 14, 28, 42, and 64 of a high-grain finishing period. Compensatory growth was evident in low-gain steers; ADG (1.50 vs. 1.11 kg/d, P < 0.05) and gain efficiency (0.221 vs. 0.109 kg/kg, P < 0.01) were greater from d 14 through 28 than for high-gain steers. Arterial base tended (P < 0.12) to be greater in low-gain than in high-gain steers, whereas calculated HCO3- (mmol/L; P < 0.20) did not differ between treatments. Arterial O2 concentration was not different (P < 0.97) between treatments but increased (P < 0.001) with increasing days on feed. Portal blood flow increased with days on feed (P < 0.001) but did not differ (P < 0.34) between treatments. Hepatic blood flow scaled to metabolic BW was 19.7% greater (P < 0.02) in low-gain than in high-gain steers. Across the feeding period, O2 consumption and CO2 flux by PDV, liver, and total splanchnic tissue (TST) did not differ (P < 0.33) between treatments. However, TST O2 consumption (mmol/[h x kg BW(0.75)]) tended (P < 0.12) to be greater in low- than in high-gain steers. Compensating steers' arterial blood acid-base measurements did not change with days on feed, indicating that they were not more susceptible to metabolic acidosis than high-gain steers. However, steers that had lower BW gain before high-grain feeding exhibited increased hepatic blood flow and TST O2 consumption (metabolic BW basis) during the finishing period compared with high-gain steers. Greater hepatic blood flow and energy expenditure by TST of previously restricted steers might have facilitated compensatory growth.

Relationship between aging and nutritionally controlled growth rate on heat production of heifers

The first objective of this study was to test how well a function that was developed to describe heat production (HP) in growing ewes fit HP data in growing heifers. The second objective was to determine the pattern of adaptation of HP to feed restriction and subsequent realimentation of nutrients. At 234.5 +/- 0.5 d of age, HP was determined by indirect calorimetry on 32 Meat Animal Research Center III heifers. Following the first calorimetry measurement, heifers on the High-High (HH) treatment continued to receive ad libitum access to feed, and daily feed offered to the Low-High (LH) heifers was set at 157 Mcal of ME/kg of BW0.75. Feed restriction of LH heifers continued for 84 d. After 84 d of restriction, LH heifers were allowed ad libitum access to feed. Heat production was determined 4 and 11 wk following feed restriction and 2, 5, 12, and 18 wk following realimentation. There was no residual bias when HP in ad libitum-fed heifers was estimated with an equation form developed in growing ewes: [(kcal/d) = f(BW, matBW) = BW (Ae[k(BW/mature BW)])], nor was there a residual bias when HP was predicted with an allometric equation: [(kcal/d) = f(BW) = A(BWk)]. However, there were residual biases when HP was estimated with an allometric equation that set the exponent to 0.75. Heat production per unit of BW of LH heifers was lower than that of HH heifers at 4 wk of feed restriction (P < 0.001), but HP did not differ between treatments at 11 wk of feed restriction (P = 0.87). At 2 (P = 0.002) and 5 wk (P < 0.001) following the increase in feed offered, HP per unit of BW of the LH heifers was greater than that of the HH heifers. Heat production did not differ between treatments at 12 and 18 wk following refeeding (P < 0.17). Our findings demonstrate that the relationship between HP and BW is described equally well by a logistic and allometric function, but applying a generalized interspecies exponent in an allometric equation to growing heifers results in a bias in estimating HP. The equation form developed in ewes can be used to develop a single equation for the prediction of HP across ages in heifers.