Empty Body Weight Gain Research Articles

190 Implementation of an updated beef energetics and body composition model in the Crop Livestock Enterprise Model (CLEM)

Abstract The Crop Livestock Enterprise Model (CLEM) is a whole-farm bioeconomic model designed to simulate and explore ruminant performance across a wide range of production systems and management strategies. The model features a flexible, component-based structure that allows users to simulate multiple types of livestock production within the same system. Animals in the model are represented on an individual basis, allowing users to explore the effects of between-animal variation on a wide range of performance metrics at the animal and farm system levels. Recently, two new features were introduced to improve ability of CLEM to represent ruminant production systems: a user-defined timestep, and a new energetics model (based on the Australian ruminant feeding standards) that adds the ability to model changes in body composition in addition to existing predictions of body weight gain and feed intake. The change in timestep from monthly to daily was required to implement the new energetics model and allows for greater ability to compare CLEM results against field data, but other timesteps (e.g., weekly) can also be used depending on user preference. The Australian ruminant feeding standards were integrated with the existing CLEM modelling framework to create a revised energetics model for CLEM capable of predicting body composition, with additional updates to prediction of relative feed intake and the effect of diet type on feed quality. The energetics model was then evaluated for prediction of feed intake (DMI), final empty body weight (EBW), and fat and protein gain (Table 1) in feedlot cattle. The evaluation dataset consisted of treatment means (n = 29) from studies of Angus or British cross steers whose body composition (fat and protein) had been measured by serial slaughter. The updated model performed well for predicting final EBW, underpredicting by 2.35 kg on average (0.55% of the observed mean). Dry matter intake was underpredicted for 80% of treatments, with mean bias averaging 1.7 kg/d across all treatments and a root mean square prediction error (RMSPE, % of the observed mean) of 25%. Data on fat and protein gain was more variable than for EBW, and the model overpredicted protein gain and underpredicted fat gain in general, with mean bias of -51 g/d (RMSPE 42%) for protein and 270 g/d (RMSPE 58%) for fat. The addition of a daily timestep and a revised energetics model add to utility of CLEM by allowing for more in-depth exploration of the effects of feeding and management over time on intake, body weight gain, and body composition. The current version of CLEM can be downloaded from the APSIM Initiative website; and an upcoming update with additional options for prediction of intake and performance for both feedlot and grazing cattle will be made available.

Growth and body composition of dairy calves fed only milk replacer at 3 intakes

Determination of energy requirements for growth depends on measuring the composition of body weight (BW) gain. Previous studies have shown that the composition of gain can be altered in young dairy calves by composition of the milk replacer diet. Here, our objective was to determine body composition and the composition of empty body gain in young calves fed increasing amounts of a milk replacer containing adequate CP. Male Holstein calves underwent an adjustment period of 14 d after birth in which they were fed whole waste milk at 10% of BW. Calves were then stratified by BW and randomly assigned to either an initial harvest group (n = 11) or to groups fed 1 of 3 milk replacer amounts and harvested after 35 d of growth. All treatments consumed the same milk replacer containing 24.8% CP (dry matter [DM] basis; from all milk proteins) and 18.9% fat, reconstituted to 12.5% solids. Treatments were milk replacer fed at 1.25% of BW (DM basis; n = 6), 1.75% of BW (n = 6), or 2.25% of BW (n = 8), adjusted weekly as calves grew. Calves fed at 1.25% or 1.75% of BW were fed twice daily and those fed 2.25% of BW were fed 3 times daily. No starter was offered. Post harvest, the bodies of calves were separated into 4 fractions: carcass; total viscera minus digesta; head, hide, feet, and tail; and blood. The sum of those 4 fractions was empty BW, which increased linearly as amount of milk replacer increased. Final heart girth and body length, but not withers height, increased linearly as intake increased. Gain:feed increased linearly with increasing milk replacer. Feeding more milk replacer increased the amounts of lean tissue and fat in the body. The percentages of water and protein in the final body decreased linearly, whereas fat percentage and energy content increased linearly as intake increased. As gain increased, the percentage of protein in gain decreased and the percentage of fat increased, resulting in an increase of energy content of EBW gain. Efficiency of energy use (retained energy:gross energy intake) increased linearly but retained energy:metabolizable energy available for growth was not different among treatments. Efficiency of protein use increased quadratically as feeding rate increased; there was no further increase at 2.25% of BW. Plasma insulin-like growth factor 1, insulin, and glucose increased linearly, whereas urea-N decreased linearly, as milk replacer intake increased. Our data document changes in body composition that affect estimates of retained energy in the bodies of calves harvested at a common age. These data are important for calculations of energy requirements for young calves.

Nonessential amino acids in tropical ruminant feed: Investigating grass and legume forages of Indonesia.

This study aimed to examine the concentration of nonessential amino acids (NEAAs) in ruminant feed in tropical areas, with a focus on forage grasses and legumes in Indonesia. A total of 11 grasses (Chrysopogon zizanioides, Brachiaria brizantha, Brachiaria humidicola, Paspalum dilatatum, Paspalum atatum, Chloris gayana, Pennisetum polystachion, Panicum maximum, Cenchrus biflorus, Andropogon canaliculatus, and Digotaria decumbens) and six legumes (Arachis hypogaea, Pueararia Javanica, Centrosema pubescens, Clitoria ternatea, and Arachis pintoi) were analyzed for NEAA content using high-performance liquid chromatography (HPLC). Based on the results of this research, it was found that almost all NEAA content in forage was less than 3% (Serine (Ser), Alanine (Ala), Glycine (Gly), Tyrosine (Tyr), Proline (Pro), Cysteine (Cys), and Asparagine (Asn), except for glutamic (Glu) acid and arginine (Arg) in some legumes. The Glu content in grass ranges from 0.76% to 2.61%, and the Arg content ranges from 0.92% to 2.09%. These two NEAAs were most abundant in grasses and legumes, with concentrations of 5.10% to 6.27% and 3.10% to 5.53%, respectively. Our study concluded that Glu and Arg were the most abundant NEAAs in tropical forages in Indonesia, with legumes having a higher concentration of NEAAs compared to grasses. Among the legumes, A. hypogaea had the highest NEAA content (23.40%), while among the forages, C. zizanioides had the highest NEAA content (12.37%). However, it was observed that neither legumes nor grasses could fulfill the metabolizable TNEAAs requirements for gaining cattle (250 kg of empty body weight gain), unlike commercial concentrates, which were found to meet the requirements, especially for Arg, Glu, and thyronine. The provision of concentrate is necessary to supplement forage to meet the NEAA needs for cattle.

Energy and protein requirements for maintenance and weight gain of Canindé goats supplemented on pasture in the semi-arid region

The purpose of this study was to estimate the carcass composition, and energy and protein requirements for maintenance and weight gain of Canindé goats supplemented on pasture in a semi-arid region. Forty-six castrated animals, with initial body weight (BW) of 15.7 ± 0.96 kg, grazing in Caatinga were used. Six animals were slaughtered at the beginning of the experiment representing the initial carcass composition (reference animals; 16.1 ± 1.15 kg BW), while the other animals were randomly distributed in four treatments (concentrate supplementation at 0%, 0.5%, 1.0%, and 1.5% BW), with ten animals per treatment. When one of the animals of each group reached 25 kg BW, all animals in that group were slaughtered. The whole empty body was weighed, ground, homogenized, and sampled for further chemical analyses. The level of supplementation influenced dry matter intake, retained energy, and body weight gain of Canindé goats. The energy (kcal/kg) and fat (g/kg EBW) contents in the carcass of goats of 15, 20, and 25 kg were 2.29 and 86.11, 2.39 and 113.48, and 2.47 and 140.53, respectively. The minimum nitrogen losses were 188 mg N/EBW0.75. The net and metabolizable energy for maintenance were 72.11 kcal/EBW0.75/day and 2.19 g/kg EBW0.75/day, respectively. The net and metabolizable protein requirements were 2.19 and 1.88 g/kg EBW0.75, respectively. The net energy and protein requirements for weight gain ranged from 2.61 to 2.81 Mcal/kg EBW gain and 194.37–222.55 g protein/kg EBW, respectively, for animals from 15 to 25 kg BW. It is concluded that the energy and protein nutritional requirements of Canindé goats supplemented on pasture in the semi-arid region vary according to body weight.

98 Utilizing gas Flux from an Automated Head Chamber System to Estimate Dietary Energy Values in Cattle Fed a Finishing Diet

Abstract Automated head chamber systems (AHCS; GreenFeed, C-Lock Inc., Rapid City, SD) provide estimates of daily flux of methane (CH4), carbon dioxide (CO2), and oxygen (O2) from free roaming cattle. This provides the opportunity to conduct energetic research from cattle in their production environment. One opportunity is to evaluate agreement between performance-estimated (P) net energy [Mcal×(kg DMI)-1] for maintenance (NEm) and gain (NEg; pNEm and pNEg, respectively) and gas-estimated (G) NEm and NEg (gNEm and gNEg, respectively). To assess this, yearling steers (n = 54; initial BW = 484.1 ± 26.0 kg) were assigned to one of two pens containing an AHCS and feed bunks designed to measure individual feed intake (Calan Gate; American Calan, Northwood, NH). Steers were transitioned to one of three finishing diets and were then fed for 80 days. Paired day initial and final unshrunk BW were measured on day 0 and 1, and on day 79 and 80, respectively. Following the feeding period, steers were transported to a commercial abattoir where carcass data were collected. Average daily gas flux was utilized to calculate heat production (HP), ignoring the energy losses from urinary nitrogen. Empty body weight (EBW) and empty body gain (EBG) were calculated and used to estimate retained energy (RE). The estimates of RE and HP were used to calculate ME intake and DMI was used to quantify dietary ME content. Through previously established cubic models, gNEm and gNEg were calculated. Ultimately, gNEm and gNEg were estimated from gas flux, DMI, ADG, and initial and final BW. A previously established quadratic model was used to estimate pNEm and pNEg using calculated energy requirements and available carcass parameters. Statistical analyses to compare the P and G energy values were conducted utilizing R (v.4.1.0) to assess precision (Pearson Correlation; r), method agreement (Lin’s Concordance Coefficient Correlation; CCC), Root Mean Square Error of Prediction (RMSEP), and Relative Prediction Error (RPE; RMSEP as a % of average performance estimated values). On average, P provided greater estimates of NEm [0.074 Mcal×(kg DMI)-1] and NEg [0.070 Mcal×(kg DMI)-1] relative to G. The G and P provided values which were highly correlated and had excellent agreement (r = 0.92, P < 0.01; CCC ≥ 0.87) for both NEm and NEg. Additionally, predictive capability was high for NEm (RMSEP = 0.12; RPE = 5.3%) and NEg (RMSEP = 0.11; RPE = 6.8%) between P and G values. The excellent agreement between P and G derived NEm and NEg values suggest that researchers can utilize AHCS to conduct energetic studies with cattle in their production environment. Moreover, the G methodology provides an alternative method for retrospective assessment of animal energetic efficiency.

Mineral composition of serially slaughtered Holstein steers supplemented with zilpaterol hydrochloride.

Calf-fed Holstein steers (n = 115; 449 ± 20 kg) were utilized in a serial harvest experiment. A baseline group of five steers was harvested after 226 d on feed (DOF), which was designated day 0. The remaining cattle were assigned randomly to 11 harvest groups, with slaughter every 28 d. Cattle were either not (CON) or were fed zilpaterol hydrochloride for 20 d followed by a 3 d withdrawal (ZH). There were five steers per treatment in each slaughter group ranging from days 28 to 308. Whole carcasses were divided into lean, bone, internal cavity, hide, and fat trim components. Apparent mineral retention (Ca, P, Mg, K, and S) within the body was calculated as the difference between mineral concentration at slaughter and day 0. Mineral concentration at day 0 was determined from body composition of steers harvested at day 0 multiplied by individual live body weight (BW) at day 0. All data were analyzed as a 2 × 11 factorial arrangement with individual animal as the experimental unit. Orthogonal contrasts were used to analyze linear and quadratic contrasts over time (11 slaughter dates). There were no differences in concentration of Ca, P, and Mg in bone tissue as feeding duration increased (P ≥ 0.89); concentration of K, Mg, and S in lean tissue did fluctuate across DOF (P < 0.01). Averaged across treatment and DOF, 99% of Ca, 92% of P, 78% of Mg, and 23% of S present in the body were in bone tissue; 67% of K and 49% of S were in lean tissue. Expressed as gram per day, apparent retention of all minerals decreased linearly across DOF (P < 0.01). Expressed relative to empty body weight (EBW) gain, apparent Ca, P, and K retention decreased linearly as BW increased (P < 0.01) whereas Mg and S increased linearly (P < 0.01). Apparent retention of Ca was greater for CON cattle (greater bone fraction) and apparent retention of K was greater for ZH cattle (greater muscle fraction) when expressed relative to EBW gain (P ≤ 0.02), demonstrating the increase in lean gain by ZH cattle. There were no differences in apparent retention of Ca, P, Mg, K, or S due to treatment (P ≥ 0.14) or time (P ≥ 0.11) when expressed relative to protein gain. Apparent retention averaged 14.4 g Ca, 7.5 g P, 0.45 g Mg, 1.3 g K, and 1.0 g S/100 g protein gain. Expressing apparent mineral retention on a protein gain basis minimized effects of rate and type of gain, allowing for better comparison across treatments and time. Feeding zilpaterol hydrochloride did not affect apparent mineral retention when expressed relative to protein gain.

PSIV-7 Evaluating Relationships Among Empty Body, Protein, and Fat Gain and Retained Energy for Pre- and Postweaning Calves

Abstract Discrepancies in the predictability of the nutritional equation used to predict empty body gain in preweaning and postweaning calves could be due to differences in proportion of protein and fat in the gain. The objective of this study was to understand the differences in the relationships of empty body weight gain (EBG) with protein (EBP) and fat (EBF) gain, and retained energy (RE) in preweaning and postweaning calves. A literature search was performed to create a dataset comprised of EBG and composition of gain in calves. The relationships of EBG with EBP, EBF, and RE was compared in preweaning and postweaning calves using R statistical software. Pearson correlation coefficients of EBG with EBP, EBF, and RE were 0.971, 0.839, and 0.934 and 0.805, 0.807, and 0.889 for preweaning and postweaning calves, respectively. A nonlinear regression model was used to evaluate the relationship between EBG and RE including the effects of age (defined as 0 for preweaning and 1 for postweaning calves) and type (defined as 0 for dairy and 1 for beef calves), [EBG = (a + b * age + c * type) * RE^ (d + e * age + f * type)]. The power coefficients were not different (P &amp;gt; 0.05) between preweaning and postweaning calves (0.379 and 0.446 ± 0.041, respectively), but the exponents were different (P ≤ 0.05; 0.921 and 0.558 ± 0.079, respectively). In conclusion, the relationship between empty body weight gain and composition of gain differs between preweaning and postweaning calves, suggesting that a more robust equation or group of equations should be used in nutrition models.

Determination of energy and protein requirements of preweaned dairy calves: A multistudy approach

The first studies concerning nutrient requirements for preweaned dairy calves were from the 1920s and 1930s; however, few studies were published in the following decades. We aimed to determine energy and protein requirements of preweaning Holstein and Holstein × Gyr dairy calves in a multistudy meta-regression. We used a database composed of individual measurements of 166 preweaned male calves (138 submitted to treatments and 28 used as the reference group) from 4 studies that used the methodology of comparative slaughter. Animals with less than 15/16 of Holstein genetic composition were considered crossbred Holstein × Gyr, whereas other animals were considered Holstein. Net energy requirements for maintenance (NEM) were determined by the regression between heat production and metabolizable energy intake (MEI). The metabolizable energy requirements for maintenance were calculated by the iterative method, and the efficiency of use of metabolizable energy for maintenance was obtained by NEM divided by the metabolizable energy requirements for maintenance. Net energy requirements for gain (NEG) were estimated using a regression of the retained energy (RE) as a function of empty body weight (EBW) and empty body gain (EBG). The efficiency of use of metabolizable energy for gain was estimated by the regression of RE as a function of MEI, but with partitioning the MEI into MEI from liquid feed and MEI from starter feed. Additionally, the effect of a liquid feed (milk or milk replacer) was tested on the slope of the regression. The metabolizable protein requirements for maintenance (MPM) were estimated using the intercept of the regression between the metabolizable protein intake (MPI) and average daily gain. The MPM was determined as the ratio between the intercept and the metabolic body weight. Net protein requirements for gain (NPG) were estimated by the regression between retained protein, EBG, and RE. The efficiency of use of metabolizable protein for gain was estimated by the regression of the retained protein as a function of MPI, but with partitioning the MPI into MPI from liquid feed and MPI from starter feed. Additionally, the effect of a liquid feed (milk or milk replacer) was tested on the regression slope. Breed did not influence any of the nutrient requirements' estimates. The NEM was estimated as 70.2 kcal/metabolic body weight per day. The efficiency of use of metabolizable energy for maintenance observed was 66%. The NEG was estimated by the equation NEG = 0.0901 × EBW0.75 × EBG0.9539. The efficiency of use of metabolizable energy for gain was estimated as 57.6, 49.3, and 41.2% for milk, milk replacer, and starter feed, respectively. The MPM was estimated as 4.22 g/EBW0.75 per day, and the NPG was determined by the equation: NPG = 30.06 × EBG + 70.98 × RE. The efficiency of use of metabolizable protein for gain was estimated as 71.9, 59.2, and 44.4% for milk, milk replacer, and starter feed, respectively. We concluded that no differences were observed in energy and protein requirements between Holstein and Holstein × Gyr crossbred cows. The efficiencies of use of metabolizable energy and protein are greater for milk when compared with milk replacer and starter feed. Therefore, we propose that the equations generated herein should be used to estimate energy and protein requirements of preweaned Holstein and Holstein × Gyr crossbred dairy calves raised under tropical conditions.

PSIV-2 Evaluation of Relationship Between Feed Efficiency Traits and Energy Metabolism Using Comparative Slaughter Studies in Growing and Finishing Cattle

Abstract There is uncertainty whether feed efficiency traits are related to energetic efficiency. The objective of this study was to utilize comparative slaughter data to evaluate the relationships of feed efficiency traits with maintenance energy requirements (MEm) and efficiency of metabolizable energy (ME) use for maintenance (km) and gain (kg). Published data were compiled (31 studies, 214 treatment means) on metabolizable energy intake (MEI) and composition of empty body gain in growing cattle. Data analyses were performed using R statistical software considering each treatment mean as an independent experimental unit. Assuming fasting heat production (FHP) varies only due to empty body protein (EBP) composition, it was computed as 295 kcal/kg EBP.75. MEm, km, and kg were computed from the nonlinear relationship between heat production and MEI. Residual intake (lower is more efficient) was computed as the residual from linear regression of MEI on EBW and EBW gain (RMEI) or MEI on EBP, retained energy as protein and retained energy as fat (RMEIc). Residual gain (higher is more efficient) was computed as the residual from linear regression of EBW gain on EBW and MEI (REBG) or retained energy on EBP and MEI (RRE). MEI was positively correlated with RMEI (0.46) and RMEIc (0.44), and EBW gain was correlated with REBG (0.58) and RRE (0.39). FHP was correlated with RMEIc (-0.25). MEm was weakly correlated with RMEI (0.19), RMEIc (0.22), and REBG (-0.26), but strongly correlated with RRE (-0.51). km was moderately correlated with RMEI (-0.35), but strongly correlated with REBG (0.49), RMEIc (-0.59), and RRE (0.79). kg was strongly correlated with RMEI (-0.69), REBG (0.47), RMEIc (-0.89), and RRE (0.70). Correlations among feed efficiency traits were strong (&amp;gt;±0.48). In conclusion, feed efficiency traits using retained energy as the dependent variable had stronger correlations with maintenance energy requirements than those using feed intake as the dependent variable.

Factorial and discriminant analysis on non-carcass components of Berganês lambs from different sexual classes and crossbreeding

AbstractThe aim of this study was to evaluate the non-carcass components (NCC) of Berganês ecotype lambs of different sexual classes and genotypes using univariate and multivariate statistics, carrying out two experimental trials. In order to evaluate the effects of the sexual class, non-castrated males (BNC), castrated males (BC) and females (BF) of Berganês ecotype lambs were used, with mean initial body weight of 27 ± 3.1 kg. To evaluate crossbreeding, non-castrated male lambs of the genotypes Berganês (BG), Berganês × Santa Inês (BSI) and Berganês × Dorper (BD) were used, as well as the control Dorper × Santa Inês (DSI), all with mean initial body weight of 28 ± 3.8 kg. The weight and yield of the total by-products was higher for BNC. Regarding the genotype, BSI showed higher weight and yield of internal fat, but the weight and yield of the total by-products was higher for BG and BD. In factorial analysis (FA), the NCC, more correlated with empty body weight (EBW) and total weight gain (TWG), showed higher eigenvectors for factor 1. For factor 2, the weights and yields of internal fat and total viscera obtained higher eigenvectors. The discriminant analysis (DA) classified 100% of individuals in their respective sexes and genotypes. Therefore, the FA indicated that, among the NCC evaluated, the weights of liver, kidneys, GIT, skin and feets are determinant for obtaining EBW and TWG. The classification achieved by the DA indicates that the sexual classes and genotypes are heterogeneous.

Animals selected for postweaning weight gain rate have similar maintenance energy requirements regardless of their residual feed intake classification.

Data of comparative slaughter were used to determine Nellore bulls' net energy requirements classified as efficient or inefficient according to residual feed intake (RFI) and selection lines (SL). Sixty-seven Nellore bulls from the selected (SE) and control (CO) lines of the selection program for postweaning weight gain were used. The animals underwent digestibility trials before being submitted to the finishing trial. Sixteen bulls were slaughtered at the beginning of the finishing trial, and their body composition was used as the baseline for the remaining animals. For body composition determinations, whole empty body components were weighed, ground, and subsampled for chemical analyses. Initial body composition was determined with equations developed from the baseline group using shrunk body weight, fat, and protein. The low RFI (LRFI) and CO animals had a lower dry matter (DMI) and nutrient intake (P < 0.05) than high RFI (HRFI) and SE animals, without alterations in digestibility coefficients (P > 0.05). During the finishing trial, DMI remained lower for LRFI and CO animals. Growth performance was similar between RFI classes, except for empty body weight gain that tended to be higher for LRFI than HRFI (P = 0.091). The SE animals had less fat content on the empty body (P = 0.005) than CO. Carcasses tended to be leaner for LRFI than HRFI (P = 0.080) and for SE than CO (P = 0.066) animals. LRFI animals retained more energy (P = 0.049) and had lower heat production (HP; P = 0.033) than the HRFI ones. Retained energy was not influenced by SL (P = 0.165), but HP tended to be higher for SE when compared to CO (P = 0.075) animals. Net energy requirement for maintenance (NEm) was lower for LRFI than HRFI (P = 0.009), and higher for SE than CO (P = 0.046) animals. There was an interaction tendency between RFI and SL (P = 0.063), suggesting that NEm was lower for LRFI+CO than HRFI+CO (P = 0.006), with no differences for SE (P = 0.527) animals. The efficiency of ME utilization for maintenance (km) of LRFI and HRFI animals were 62.6% and 58.4%, respectively, and for SE and CO were 59.0% and 62.1%, respectively. The breeding program for postweaning weight has not improved feed efficiency over the years, with RFI classification not being a promising selection tool for SE animals. Classification based on RFI seems to be useful in animals that have not undergone the breeding program, with LRFI animals having lower energy requirements than the HRFI ones.

Breeding strategies in evaluation of forage barley

AbstractProducers on the Canadian Prairies grow barley (Hordeum vulgare L.) as a forage crop for ruminants, especially cattle. The purpose of our study was to determine methods to improve our selection of barley lines with superior forage value for ruminants. Data from the Western Cooperative Forage Barley Registration Test were used with permission of the Prairie Recommending Committee for Oat and Barley (PRCOB) and the breeders. Data were analyzed from 20 environments collected from 3 yr (2012–2014) and seven sites. We measured forage accumulation (FA) at the soft dough stage, five nutritive value traits, and three derived cow–calf variables. Although the variation in FA and forage nutritive value traits attributed to environment (E) was large, significant genotypic (G) effects were found for all traits measured. Whereas G× E effects were also significant, the mean square effect for G was up to 40 times higher than the mean squares for G×E. The proportion of variance attributed to G was greater for nutritive value traits than for FA. Significance of G means there was variability in the germplasm tested, and improvement through selection should be possible. The two parametric methods of stability analyses (Francis–Kannenberg method and Eberhart–Russell method) often identified the same lines as superior. Lines that were superior for FA and carrying capacity (cow on swath grazing, CC) were often different from those identified as superior for nutritive value, empty body weight gain (cow, EBWG) and average daily gain (backgrounding calf, ADG). A nonparametric method used to determine dynamic stability (Nassar–Hühn method) identified different lines as superior from the parametric methods. Breeders can use a combination of these selection criteria in breeding forage barley varieties with enhanced forage value for ruminants.

Mineral requirements for weight gain in growing male Santa Inês and Morada Nova hair sheep.

This study estimated the net macro and micromineral requirement from the 48 male uncastrated lambs (24 growing male Santa Inês and 24 growing male Morada Nova hair sheep), with initial weights of 21.7 ± 1.2kg and 20.8 ± 0.8kg using the comparative slaughter method. The experimental diet consisted of 30% forage (Buffel-Cenchrus ciliaris (L) hay) and 70% concentrate (corn grain 43.5%, soybean meal 22.0%, vegetable oil 3.0% and mineral supplement 1.5%). The experimental design was a completely randomized with two breeds, four weights, and six replicate. Mineral requirements sufficient to promote weight gain in Santa Inês sheep ranged from 1.75 to 1.03 g Ca, 1.01 to 0.61 g of P, 0.38 to 0.21 g of K, 0.38 to 0.16 of Na, 0.10 to 0.06 Mg, 28.5 to 16.0mg of Fe, 6.14 to 3.22 mg of Cu, and Zn 23.0 to 14.0mg/kg per unit of empty body weight (EBW) gain. In the Morada Nova breed, the requirements ranged from 1.96 to 0.84 g of Ca, 1.15 to 0.46 of P, 0.39 to 0.19 of K, 0.28 to 0.13 of Na, 0.10 to 0.05 Mg, 26.2 to 12.9mg of Fe, 5.59 to 2.46 Cu, and Zn 23.6 to 10.3mg/kg of EBW gain. Mineral requirements varied mainly in accordance with the proportion of bone mass and fat concentration in the carcass, which were influenced by the slaughter weight of the animals, and therefore should be used in the formulation of dietary mineral supplements.

Development of equations to predict carcass weight, empty body gain, and retained energy of Zebu beef cattle

The accurate supply of energy is essential to optimize livestock productivity and profitability. Furthermore, replacing empty BW gain (EBG) with carcass gain (CG) might be a suitable alternative to estimate the retained energy (RE) of beef cattle. Thus, this multi-analysis study was conducted aiming to estimate and validate new equations to predict carcass weight (CW), EBG, and RE of Zebu, beef crossbred, and dairy crossbred. A database composed by 1112 animals encompassing bulls, steers, heifers of different genetic groups (Zebu, beef crossbred, and dairy crossbred), and two types of slaughter plants (commercial and experimental) was used for generating the new CW equation. For the development of the EBG and RE equations, a database of 636 observations composed of bulls, steers, and heifers of different genetic groups (Zebu, beef crossbred, and dairy crossbred) was assembled. The validation of new equations was performed using independent databases composed by 137 observations (80 for CW and 57 for EBG and RE). The new approaches for EBG and RE validation also included data from our research group studies (Inside) and independent data from literature publications (Outside). Furthermore, the new RE equation was compared to the current model devised by the nutritional requirements, diet formulation, and performance prediction of Zebu and crossbred cattle (BR-CORTE, 2016). Validation analyses were performed by using the Model Evaluation System (MES; 3.1.13, College Station, US). The CW was accurately estimated by the new equation when using both commercial and experimental data. Also, the equations developed in this study accurately estimated EBG and RE using both inside and outside data. In conclusion, equations proposed in this study accurately and precisely estimated CW, EBG, and RE of Zebu beef cattle that composed validation data set. Therefore, we suggest the following equations to estimate CW, EBG, and RE of Zebu cattle: CW, kg = −11.0±1.56 + P + ((0.609±0.005 + G + B) × SBW); EBG (kg) = 0.044±0.017 + 1.47±0.026 × CG; RE (MJ/d) = 4.184 × (0.082±0.002 × EQEBW0.75 × CG0.777±0.039), where P = slaughter plant effect, if commercial = −10.98, if experimental =0; G = gender effect, if steer = 0, if bull = 0.008169 and if heifer = −0.00612; B = genotype effect, if Zebu = 0, if dairy crossbreds = −0.03301 and if beef crossbreds = −0.01595; SBW = shrunk BW; CG = carcass gain; EQEBW = equivalent empty BW.

Influence of starter crude protein content on growth and body composition of dairy calves in an enhanced early nutrition program

Our objectives were to determine the effect of starter crude protein (CP) content on body composition of male Holstein calves from birth to 10 wk of age in an enhanced early nutrition program, and to compare the enhanced program to a conventional milk replacer program. Calves (n = 45) were purchased on the day of birth and assigned to a randomized block design. Eight calves were harvested at baseline and remaining calves were divided among the following 3 dietary treatments: (1) low rate of milk replacer [LMR; 20.6% CP, 21.7% fat; 1.25% of body weight (BW) as dry matter (DM)] plus conventional starter (CCS; 21.5% CP, DM basis); n = 11 calves; (2) high rate of milk replacer (HMR; 29.1% CP, 17.3% fat; 1.5% of BW as DM for wk 1, 2% of BW as DM wk 2-5, 1% of BW as DM wk 6) plus conventional starter; n = 12 calves; and (3) enhanced milk replacer (HMR) plus high-CP starter (HCS; 26% CP, DM basis); n = 14 calves. A subset of calves (n = 8) was harvested on d 2 to provide baseline data. Calves began treatments on d 2 or 3 of age. Calves were weaned at d 42. Starter was available ad libitum. Calves from each treatment were harvested at 5 (n = 18) and 10 (n = 19) wk of age and divided into 4 fractions: carcass; viscera; blood; and head, hide, feet, and tail. Fractions were analyzed for energy, CP, lipid, and ash. Average weekly starter intake did not differ between enhanced treatments. Gain of BW was greater for calves fed HMR than for LMR, but was unaffected by starter CP. Carcass weights at 5 wk were greater for HMR but did not differ between starter CP content. At 10 wk, carcass weights were heavier for HMR and had a greater percentage of empty BW for HMR + CCS than for HMR + HCS. At 10 wk, the weights of reticulorumen and liver were greater for calves fed HMR + HCS than for those fed HMR + CCS. At 5 wk, empty BW gain for HMR contained more water and less fat and ash than in calves fed LMR. At 10 wk, empty BW gain for calves fed HMR + HCS contained a greater percentage of water and less fat than for calves fed HMR + CCS. Plasma β-hydroxybutyrate was greater after weaning for calves fed HMR + HCS than for those fed HMR + CCS. After weaning, calves fed HMR had greater plasma total protein concentration than those fed LMR, and total protein was greater for calves fed HMR + HCS than those fed HMR + CCS. Plasma urea N was greater for calves fed HMR treatments, and postweaning was greater for calves fed HMR + HCS. A high-CP starter had minimal effect on empty BW gain before weaning, but after weaning it tended to increase mass of reticulorumen and liver.

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.

Weight adjustment equation for hair sheep raised in warm conditions

To estimate the nutritional requirements of hair sheep, knowledge about the animal’s weight and its relationships with growth performances is essential. A study was carried with the objective to establish the relationships between BW, fasting BW (FBW), empty BW (EBW), average daily gain (ADG) and empty BW gain (EBWG) for hair sheep in growing and finishing phases in Brazilian conditions. Databases were obtained from 32 studies, for a total of 1145 observations; there were 3 sex classes (non-castrated male, castrated male and female) and 2 feeding systems (pasture and feedlot). The most representative breeds in the database were Santa Ines (n = 473), Morada Nova (n = 70) and Brazilian Somali (n = 47). The other animals in the database were crossbreeds (n = 555). The FBW (kg), EBW and EBWG (kg/day) were estimated according to linear regression. A random coefficient model was adopted, considering the study as a random effect and including the possibility of covariance between the slope and the intercept. The coefficients obtained from the linear regression of the FBW against the BW, EBW against the FBW and EBWG against the ADG did not differ between sex class (P > 0.05) and genotype (P > 0.05). The equations generated to estimate FBW from the BW, EBW from the FBW and EBWG from the ADG are as follows: FBW = −0.5470 (±0.2025) + 0.9313(±0.019) × BW, EBW = −1.4944 (±0.3639) + 0.8816 (±0.018) × FBW and EBWG = 0.906 (±0.019) × ADG, respectively. The low mean squared error values found in the cross-validation confirmed the reliability of these equations. Considering a sheep with a BW of 30 kg and a 100 g ADG, the estimated FBW, EBW and EBWG calculated using the generated equations are 27, 22.65 and 0.090 kg, respectively. In conclusion, the generated equations can be used in growing hair sheep. The validation procedure applied to the generated equations showed that its use for hair sheep seems to be appropriate.

Genotype effects on energy and protein requirements in growing male goats

Goat genotype may alter the net energy and protein requirements for maintenance (NEm and NPm, respectively) and weight gain (NEg and NPg).This study was designed to investigate and quantify the effect of goat type on NEm, NPm, NEg and NPg, and quantify the net requirements for energy and protein for dairy, meat and indigenous growing male goats. For that, comparative slaughter studies were gathered and a meta-analytical approach was used. Two distinct databases were organized: one composed of 233 individual records from 11 studies of meat (n = 81), dairy (n = 97) and indigenous (n = 55) growing male goats weighing from 4.50 to 51.0 kg, to depict NEm and NPm; and another database composed of 239 individual records from nine studies of meat (n = 87), dairy (n = 97) and indigenous (n = 55) growing male goats weighing from 4.30 to 51.0 kg, to depict NEg and NPg. Our findings showed that NEm of meat goats was 8.5% greater (336 ± 10.8 kJ/kg0.75 of empty BW; EBW) than dairy and indigenous goats (310 ± 8.20 kJ/kg0.75 EBW; P < 0.05). Whereas, NPm was not affected by goat type (1.92 ± 0.239 g/kg EBW; P = 0.91). The NPg was 185.1 ± 1.82 g/kg of EBW gain for goats weighing 5 kg BW and 192.5 ± 4.33 g/kg of EBW gain for goats weighing 45 kg BW, and thus did not change across goat type (P = 0.12). On the other hand, NEg increased from 7.29 ± 0.191 to 11.9 ± 0.386 MJ/kg of EBW in male dairy goats, and from 7.32 ± 0.144 to 15.7 ± 0.537 MJ/kg of EBW in meat and indigenous growing male goats weighing between 5 and 45 kg BW. When body protein was used as a predictor in the allometric equation instead of EBW seeking to account for the degree of maturity, goat type differences disappeared; however, this predictor showed a high variation among individuals. In conclusion, energy and protein requirements for gain in distinct goat types reflect on body composition differences. Future research should focus on better understanding the maturity degree and its consequences in the energy requirement of growing male goats and better depict the goat type effect on it, as well as on the efficiency of utilization.

Energy and protein requirements of woolless sheep under tropical conditions

The objective of this study was to determine the energy and protein requirements for maintenance and weight gain of growing woolless sheep and, in addition, to estimate the shrunk body weight (SBW) and empty body weight (EBW) of the animals according to their body weight (BW) in the fed state. Data from 150 animals from three comparative slaughter experiments with confined castrated sheep averaging 5 ± 0.96 months of age and similar BW (20.74 ± 2.99 kg) were used. Three models were evaluated to estimate EBW from SBW: linear, linear with intercept and non-linear. The following requirements were estimated: net energy for maintenance (NEm), metabolizable for maintenance (MEm), net energy for gain (NEg), efficiency of use of metabolizable energy for gain, metabolizable protein requirement for maintenance (MPm), net protein requirement for gain (NPg), and efficiency of use of metabolizable protein for gain (k). Fasting losses corresponded to 6.18% of BW and the better model to establish the relationship between SBW and EBW was nonlinear. The NEm and MEm were 70.44 and 109.34 kcal/kg EBW0.75/day, respectively. For NEg, the adjusted model was based on the ratio of the energy retained as a function of the EBW and the desired empty body weight gain (EBG). Considering two lambs weighing 15 kg and 30 kg with a daily gain of 100 g, the estimated NEg is 181 and 360 kcal/kg EBW0.75/day, respectively. The estimated kg was 0.407. For MPm, the value of 3.19 g/kg EBW0.75/day was estimated. The estimated NPg for animals of 15 and 30 kg, with the same gain rate was 13.13 and 13.61 g/day, respectively, which corresponds to the protein concentration in gain of 170 and 161 g/kg EBG, and efficiency of use of the metabolizable protein for gain ranging from 0.66 to 0.41. The nutritional requirements of woolless sheep did not follow the standards assumed by the international feeding systems, except for the energy requirements for maintenance and efficiency of use of the metabolizable energy for maintenance, which did not differ. The losses represented by the gastrointestinal tract (GIT) after fasting and slaughtering periods are higher in woolless sheep compared to those presented by the international feeding systems.

Limit feeding as a strategy to increase energy efficiency in intensified cow-calf production systems.

Two experiments were conducted to measure efficiency of energy use in limit-fed cows. In Exp. 1, 32 pregnant, crossbred cows were used to examine the effects of dietary energy concentration and intake level on energy utilization and digestion. In a 2 × 2 factorial treatment arrangement, cows received diets formulated at either 1.54 Mcal NEm/kg high energy (H) or 1.08 Mcal NEm/kg low energy (L); amounts of each diet were fed at amounts to achieve either 80% (80) or 120% (120) of maintenance energy requirements. Fecal grab samples were collected on days 14, 28, 42, and 56 for determination of energy digestion and metabolizable energy (ME) intake. Acid detergent insoluble ash and bomb calorimetry were used to estimate fecal energy production. Cow body weight and 12th rib fat thickness were used to estimate body energy, using 8 different methods, at the beginning and end of a 56-d feeding period. Energy retention (RE) was calculated as the difference in body energy on days 0 and 56. Heat energy (HE) was calculated as the difference in ME intake and RE. Energy digestion increased (P = 0.04) with intake restriction. Cows consuming H tended to have greater (P = 0.08) empty body weight (EBW) gain than cows consuming L, but no difference was observed (P = 0.12) between cows fed 120 compared with cows fed 80. Estimates of HE were greater for L than H (P < 0.01) and greater for 120 than 80 (P < 0.01), such that estimated fasting heat production of H (57.2 kcal/kg EBW0.75) was lower than that of L (73.3 kcal/kg EBW0.75). In Exp. 2, 16 ruminally cannulated, crossbred steers were used to examine the effects of dietary energy concentration and intake level on energy digestion. Treatment arrangement and laboratory methods were replicated from Exp. 1. Following a 14-d adaptation period, fecal samples were collected, such that samples were represented in 2-h intervals post-feeding across 24 h. Diet × intake interactions were observed for nutrient digestibility. Energy digestibility was greater in steers fed H than in steers fed L (P < 0.01); however, digestibility of each nutrient increased by approximately 10% in steers fed H80 vs. those fed H120 (P ≤ 0.03); nutrient digestibility was similar among levels of intake in steers fed L (P = 0.54). These results suggest that intake restriction may increase diet utilization and that the magnitude of change may be related to diet energy density.