Post-weaning Weight Research Articles

Comparison of machine learning algorithms and multiple linear regression for live weight estimation of Akkaraman lambs

This study was designed to predict the post-weaning weights of Akkaraman lambs reared on different farms using multiple linear regression and machine learning algorithms. The effect of factors the age of the dam, gender, type of lambing, enterprise, type of flock, birth weight, and weaning weight was analyzed. The data was collected from a total of 25,316 Akkaraman lambs raised at multiple farms in the Çiftlik District of Niğde province. Comparative analysis was conducted by using multiple linear regression, Random Forest, Support Vector Machines (and Support Vector Regression), Extreme Gradient Boosting (XGBoost) (and Gradient Boosting), Bayesian Regularized Neural Network, Radial Basis Function Neural Network, Classification and Regression Trees, Exhaustive Chi-squared Automatic Interaction Detection (and Chi-squared Automatic Interaction Detection), and Multivariate Adaptive Regression Splines algorithms. In this study, the test dataset was divided into five layers using the K-fold cross-validation method. The performance of models was compared using performance criteria such as Adjusted R-squared (Adj-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document}), Root Mean Square Error (RMSE), Mean Absolute Deviation (MAD), and Mean Absolute Percentage Error (MAPE) by utilizing test populations in the predicted models. Additionally, the presence of low standard deviations for these criteria indicates the absence of an overfitting problem. \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document}The comparison results showed the Random Forest algorithm had the best predictive performance compared to other algorithms with Adj-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document}, RMSE, MAD, and MAPE values of 0.75, 3.683, 2.876, and 10.112, respectively. In conclusion, the results obtained through Multiple Linear Regression for the live weights of Akkaraman lambs were less accurate than the results obtained through artificial neural network analysis.

Genetic parameter estimates for growth traits in Texel sheep of Brazil

The present study aimed to estimate the genetic parameters for direct and maternal influences on birth weight (BW), weaning weight (WW) and postweaning weight (PW) of Texel sheep, raised in an extensive system from Brazil. Data file used in this study consisted of 834 body weight records of 834 Texel lambs (376 males and 458 females) born from 2020 to 2021, offspring of 475 ewes and 45 rams. Multivariate animal model was conducted to estimate the variance components, heritability and genetic correlations using the restricted maximum likelihood method in ASReml-R software, while the effects of fixed factors were analyzed by the general linear model procedure of statistical analysis system. Five different animal models, with or without maternal genetic effect, maternal permanent environment effect and covariance between additive genetic and maternal genetic effects, were fitted on the growth traits data of the Texel sheep population. AIC and BIC test results were used to evaluate the best fit models for growth traits. The effect of lamb's sex was significant on BW, WW and PW while birth type and year of lambing effects were on all traits (P < 0.05). Model 4, incorporating direct additive genetic, maternal additive genetic and maternal permanent environmental effects showed the minimum AIC estimate for all growth traits. The direct additive genetic heritability for BW, WW and PW were 0.11 ± 0.03, 0.37 ± 0.05 and 0.31 ± 0.08, respectively and maternal heritability for these traits were 0.00 ± 0.00, 0.04 ± 0.02 and 0.00 ± 0.00, respectively. The total heritability estimates for BW, WW and PW were 0.11 ± 0.03, 0.39 ± 0.05 and 0.31 ± 0.08, respectively. The estimates of the direct additive genetic correlation between BW-WW, BW-PW and WW-PW were 0.68 ± 0.12, 0.66 ± 0.12 and 0.78 ± 0.07, respectively. The maternal permanent environmental correlation between BW-WW, BW-PW and WW-PW were 0.38 ± 0.27, 0.29 ± 0.20 and 0.74 ± 0.16, respectively. Phenotypic correlation ranged from 0.43 ± 0.03 to 0.75 ± 0.02. It is concluded that due to the existence of genetic variation for BB, WW and PW and strong genetic correlation among them, genetic progress for these traits is possible by selection in Texel sheep from Brazil.

Genome-wide association study considering genotype-by-environment interaction for productive and reproductive traits using whole-genome sequencing in Nellore cattle

BackgroundThe genotype-by-environment interaction (GxE) in beef cattle can be investigated using reaction norm models to assess environmental sensitivity and, combined with genome-wide association studies (GWAS), to map genomic regions related to animal adaptation. Including genetic markers from whole-genome sequencing in reaction norm (RN) models allows us to identify high-resolution candidate genes across environmental gradients through GWAS. Hence, we performed a GWAS via the RN approach using whole-genome sequencing data, focusing on mapping candidate genes associated with the expression of reproductive and growth traits in Nellore cattle. For this purpose, we used phenotypic data for age at first calving (AFC), scrotal circumference (SC), post-weaning weight gain (PWG), and yearling weight (YW). A total of 20,000 males and 7,159 females genotyped with 770k were imputed to the whole sequence (29 M). After quality control and linkage disequilibrium (LD) pruning, there remained ∼ 2.41 M SNPs for SC, PWG, and YW and ∼ 5.06 M SNPs for AFC.ResultsSignificant SNPs were identified on Bos taurus autosomes (BTA) 10, 11, 14, 18, 19, 20, 21, 24, 25 and 27 for AFC and on BTA 4, 5 and 8 for SC. For growth traits, significant SNP markers were identified on BTA 3, 5 and 20 for YW and PWG. A total of 56 positional candidate genes were identified for AFC, 9 for SC, 3 for PWG, and 24 for YW. The significant SNPs detected for the reaction norm coefficients in Nellore cattle were found to be associated with growth, adaptative, and reproductive traits. These candidate genes are involved in biological mechanisms related to lipid metabolism, immune response, mitogen-activated protein kinase (MAPK) signaling pathway, and energy and phosphate metabolism.ConclusionsGWAS results highlighted differences in the physiological processes linked to lipid metabolism, immune response, MAPK signaling pathway, and energy and phosphate metabolism, providing insights into how different environmental conditions interact with specific genes affecting animal adaptation, productivity, and reproductive performance. The shared genomic regions between the intercept and slope are directly implicated in the regulation of growth and reproductive traits in Nellore cattle raised under different environmental conditions.

Effects of inbreeding on production traits and genetic evaluations in Guzerá beef cattle raised under tropical conditions.

The objectives of this study were to evaluate the influence of inbreeding on growth traits and body measurements, as well as on the estimation of genetic parameters and genetic trends in Guzerá cattle. Phenotypic records of 4,212 animals selected for postweaning weight from Guzerá Breeding Program of Advanced Beef Cattle Research Center were utilized. The pedigree file contained records from 7,213 animals born from 1928 to 2019. The traits analyzed were: birth weight (BW), weights adjusted to 210, 378 and 550 days of age (W210, W378 and W550, respectively), chest girth at 378 and 550 days of age (CG378 and CG550), scrotal circumference (SC), and hip height at 378 and 550 days of age (HH378 and H550). Linear regression was used to evaluate the effects of inbreeding on traits. Genetic parameters were obtained using models including or not the effect of inbreeding as a covariate. Inbreeding had negative effects (P ≤ 0.01) on BW (-0.09kg), W378 (-2.86kg), W550 (-2.95kg), HH378 (-0.10cm), and H550 (-0.29cm). The lowest and highest heritability estimates were obtained for W210 (0.21 ± 0.07) and HH550 (0.57 ± 0.06), respectively. The genetic correlations were strong and positive between all traits, ranging from 0.44 ± 0.08 (SC x HH) to 0.99 ± 0.01 (W378 x W550). Spearman correlations between EBVs obtained with or without inbreeding effect ranged from 0.968 to 0.995 (P < 0.01). The results indicate loss of productive performance in inbred animals. However, the inclusion of inbreeding coefficient in genetic evaluation models did not alter the magnitude of genetic parameters or genetic trends for the traits studied.

Genetic parameters for visual scores, growth and carcass traits in Nellore Cattle.

Growth and carcass traits are essential selection criteria for beef cattle breeding programs. However, it is necessary to combine these measurements with body composition traits to meet the demand of the consumer market. This study aimed to estimate the genetic parameters for visual scores, growth (pre and post-weaning weights), and carcass (rib eye area (REA), back and rump fat thickness) traits in Nellore cattle using Bayesian inference. Data from 12,060 animals belonging to the HoRa Hofig Ramos herd were used. Morphological traits were evaluated by the MERCOS methodology. The heritability estimates obtained ranged from low to high magnitude, from 0.15 to 0.28 for visual scores, 0.13 to 0.44 for growth, and from 0.42 to 0.46 for carcass traits. Genetic correlations between visual scores and growth traits were generally of moderate to high magnitudes, however, visual scores showed low correlations with carcass traits, except between sacral bone and structure and REA. Selection for visual score traits can lead to favorable responses in body weight and vice versa, but the same is not true for carcass traits. Morphological categorical traits can be used as complementary tools that add value to selection.

Factors Affecting Post-Weaning Growth of Boer and Boer Cross Goats in a Closed Breeding Farm Population

This study aimed to analyze the factors affecting the post-weaning growth of Boer and Boer cross goats in a closed breeding farm population. A total of 1,083 female kids were selected from a record of 1,501 weaned kids produced by mating Boer bucks with Boer does, Jawarandu does, and Boer × Jawarandu does. The data collected at a private company's goat farm represent a closed breeding population from January 2013 to January 2016. The data were selected based on the weaning weight and at least one post-weaning weight at approximately 6, 9, or 12 months. Two-step linear models were applied: complete model and reduced model. The complete model factors included genetic group, buck, litter size, birth season, weaning season-year, and their interactions. The reduced model included only significant factors and two-way interactions. The results showed that the genetic group, bucks, litter size, birth season, and weaning season-year significantly affected Boer and Boer cross goats' post-weaning weight and average daily gain. Additionally, interactions between the genetic group with the buck, litter size, and birth season were observed. In conclusion, genetic and non-genetic factors significantly influence the post-weaning growth of Boer and Boer cross goats. Non-genetic factors should be considered in the model and selection to achieve optimal goat performance.

Relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls: a cross sectional study.

The aim of this study was to investigate the relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls selected for postweaning weight. Data from the andrological evaluation of 836 bulls born between 2000 and 2019, including 583 Nellore animals (Bos indicus) and 253 Caracu animals (Bos taurus), were used. The bulls were divided into categories of age at the time of assessment: category 1 consisted of animals aged 20 to 23months (22 ± 0.76months, 518 ± 94.17kg), category 2 consisted of animals aged 24 to 35months (30 ± 4.42months, 679 ± 137.19kg), and category 3 consisted of animals ≥ 36months (60 ± 14.12months, 907 ± 161.73kg). The statistical model included the effects of breed, age category, date of semen collection, and breed x age category interaction. Heritability estimates for scrotal circumference at 13months of age (SC1year) and semen quality traits were obtained for the sample of Nellore animals. Most semen quality traits improved with increasing age in both Nellore and Caracu animals. High heritability was observed for SC1year (0.45), while sperm motility, vigor, turbulence, and major, minor and total sperm defects exhibited low heritability (0.11, 0.019, 0.047, 0.017, 0.017 and 0.019, respectively). Spearman correlations of breeding values for postweaning weight (W378) and SC1year with the semen quality traits were low. Nellore and Caracu bulls have similar semen quality that improves with increasing age. In the Nellore breed, the heritability of SC is high, while semen quality traits exhibit low heritability. Selection for higher postweaning weight does not phenotypically affect the semen quality of bulls at breeding age.

PSVII-5 Detection and Characterization of Copy Number Variation Regions in Three Selection Lines of Nellore Cattle

Abstract Copy number variations (CNV) can partially explain phenotypic variability in complex traits. Therefore, we aimed to identify and characterize CNV regions (CNVR) in Nellore cattle from three selection lines. These selection lines were established in 1981 and consist of a line selected based on heavier postweaning weight (NeS, n = 245), a line selected based on heavier postweaning weight and reduced residual feeding Intake (NeT, n = 556), and a line selected based on average postweaning weight (NeC, n = 114). Genotypes (GGP Indicus HD and GGP Indicus 50K panel) of 928 animals were analyzed. The CNV identification was performed per SNP panel using the PennCNV software. After identifying the CNVs, quality control was performed and the following exclusion criteria were used: Log R ratio &amp;gt; 0.30, B allele frequency "drift” &amp;lt; 0.01, and guanine-cytosine wave factor &amp;lt; 0.05. CNVR were determined by grouping individual CNVs with at least one overlapping base pair. The exclusive regions present in at least 10% of the animals from each population were identified. The GALLO R package was used for the annotation of genes in these regions, and the WebGestaltR package was used for the Gene Ontology analyses. Eight-hundred-and-twenty-three CNVRs (143 losses, 650 gains, and 30 mixed), 1,493 CNVRs (327 losses, 1,113 gains, and 53 mixed), and 482 CNVRs (90 losses, 378 gains, and 14 mixed) were identified in the NeS, NeT, and NeC lines, respectively. The CNVRs covered 1.61%, 2.54%, and 0.94% of the cattle genome in NeS, NeT, and NeC, respectively. Only 32 CNVRs were identified in at least 10% of the animals in NeS, 33 in NeT, and 25 in NeC. Of these regions, 2 are NeS exclusive, 4 are NeT exclusive, and 6 are NeC exclusive. Eight candidate genes in NeS, 20 candidate genes in NeT, and 16 genes in NeC overlapped with the exclusive regions. We identified some important genes such as SLC15A1 in NeS herd that have functions associated to nutrient absorption, MAPK1 identified in the NeT population is involved in a wide variety of cellular processes such as proliferation, differentiation, transcription regulation and development, and IQCA1L in the NeC population is involved in ATP activity. The genes identified are involved in 5 biological processes, such as response to growth factor, in NeT, and in 1 biological process (response to endoplasmic reticulum stress) in NeC. The differences observed in CNVR improve our understanding of the genetic architecture of the three Nellore selection schemes, given that the identification of genes in the CNVR allows the identification of genomic regions and biological processes that could be associated with the phenotypic differences between selection lines.

PSV-23 Characterization of Katahdin Lamb Carcasses in a Traditional Lamb Marketing Context

Abstract The Katahdin breed has grown in popularity in the US, but it is relatively unknown if their carcasses conform to expectations of the traditional commodity lamb industry. Purebred Katahdin wethers (n = 223) were sourced from the genetic reference flock at the U.S. Meat Animal Research Center over two consecutive years. The flock is enrolled in the National Sheep Improvement Program (NSIP) and estimated breeding values (EBV) were available on standard production traits. Lambs were assigned to one of three groups per year based on body weight (BW) and fed a common finishing diet through harvest at similar end BW (51.3 ± 5.6 kg) but varying age (223.8 ± 32.2 d). Lambs were harvested at a commercial processor, hot carcass weight (HCW) was recorded, dressing percentage (DP) was calculated, and carcasses were chilled for 24 h. Carcasses were then ribbed and 12th rib backfat thickness (BFT), and loin muscle area (LMA) were measured. Traits were analyzed in mixed models with fixed class effects of finishing group (6 levels) and rearing type (single or multiple), a linear covariate of harvest age, and a random effect of sire (n = 16). There were no differences in BW, HCW, BFT, and LMA between rearing types but lambs reared as multiples had greater DP than those reared as singles (P = 0.02; Table). End BW increased while DP decreased with lamb harvest age (P ≤ 0.03). Pearson correlation coefficients were estimated between traits including post-weaning weight (PWWT) NSIP EBV. There was a strong, positive correlation between HCW and BFT (0.52) and HCW and BWT (0.54; P &amp;lt; 0.001). In contrast, HCW was only moderately correlated to LMA (0.35; P &amp;lt; 0.001). The PWWT EBV is the best genetic predictor of post-weaning lamb growth and was moderately correlated with end BW (0.38), HCW (0.35), and LMA (0.35; P &amp;lt; 0.001). Traditional markets prefer carcasses to be 29.5 – 36.3 kg HCW and &amp;lt; 6.4 mm BFT; 91% and 51% of Katahdin carcasses were below the HCW and BFT thresholds, respectively. Katahdins are capable of producing lean carcasses that conform to packer ideals for BF when fed to harvest BW of the present study, which may reduce excess fat trimming during fabrication. However, HCW observed in the present study may suggest greater suitability for non-traditional (i.e., ethnic) markets. Lower correlations between carcass traits in Katahdin compared with past research in Western white-faced lambs may highlight important biological differences in growth and fat deposition among divergent breed types. Crossbreeding Katahdin ewes with terminal sire breeds and within breed selection will improve growth and carcass traits without exceeding HCW thresholds commonly reached in wool sheep but should be considered in tandem with other breeding objectives.

Meta-analysis: the effect of feeding indigofera leaves (Indigofera zollingeriana) on goat livestock performance

This study aimed to determine the effect of Indigofera leaves feeding (Indigofera zollingeriana) on the performance of goat livestock using meta-analysis studies. This research begins with integrating secondary data from various publications, getting journals and proceedings sources in PubMed, GS. The publications selected must contain information on the effect of feeding Indigofera leaves on goats. Furthermore, the data were collected into a database using Microsoft Excel. During data collection, experimental units of each data were equated, then analyzed using R version 4.2.0. The results of the analysis showed that the effect of feeding Indigofera leaves was not significant effect on ADG (average daily gain), PWW (post-weaning weight), and FCR (feed conversion rate). However, the impact was substantial (P<0.05) on feed consumption or DMI (dry matter intake). This indicates that goats favor Indigofera leaf feed, and can be used as a good forage legume to improve goat performance.

Breeding objectives for Central Highland goats using participatory and bio-economic modelling approaches.

The breeding objectives of Central Highland goats rearing under a low-input production system were defined through a participatory proportional piling method and bio-economic model. Additionally, the economic values and relative economic value of the breeding objective traits were derived. A participatory proportional piling method was used to estimate the relative weights of farmers attached to a list of goat traits identified, and the relative weights were statistically evaluated using a generalized multinomial logit model analysis. A bio-economic model was used to compute the economic values of the identified traits. The most important traits for selection of does according to farmer's preference were body size, coat colour, post-weaning growth rate and weaning rate with a relative weight (odds ratio) of 1.58, 1.38, 1.37 and 1.13, respectively. Goats with dark red followed by light red coat colour were the most preferred (p < 0.001) by goat keepers compared with white-coloured goats. Farmers were more likely (p < 0.001) to allocate higher scores for does-bearing twins than for single and triplet-bearing does. Using the bio-economic model (economic value and relative economic value), post-weaning growth rate, weaning rate, and six-month weight (body size) were identified as the most important traits and if the mean of these traits is changed by one genetic standard deviation, the change in profit will range from 2.06 to 3.03 $ doe-1 year-1 . Therefore, the most important traits for the selection of Central Highland goats according to the economic-based method were post-weaning weight gain, weaning rate and body size (six-month weight). Besides, coat colour was the second preferred trait by goat keepers next to body size. Thus, this aesthetical trait should be included in the designed breeding programme besides economically important quantitative traits. The combination of the participatory proportional piling method and bio-economic model would give better insights to explore the trait preferences of farmers and enhance profitability. The economic values of traits estimated in this study can be used for the construction of selection indices for Central Highland goats.

Evaluation of the productive performance of Colombian hair sheep based on growth traits

Contextualization: Colombian hair sheep [CHS] are animals of great importance, because their genetic material has been adapting for more than 500 years to the environment; besides, these animals have a transcendental role in Colombia for their contribution to food security and family economy. However, a great part of the sheep production in the country presents low production parameters. Knowledge gap: ignorance of Colombian hair sheep (CHS) biotypes’ productivity has led to the undervaluation of the genetic resource found in these animals, accompanied by insufficient efforts to improve sheep production systems. Purpose of the study: determine the productive performance of three biotypes of Colombian hair sheep. Methodology: this study was conducted in these biotypes of hair sheep: Ethiopian [CHSE] (40 individuals), Sudan [CHSS] (60) and Creole crossed with Pelibuey [CHSP] (60). Five growth traits [birth weight, adjusted weaning weight at 90 days, adjusted final weight at the age of 1 year, and pre-weaning and post-weaning weight gain] were evaluated. Descriptive statistical and variance analysis were performed based on variables such as sex, farm, type of birth, parent, and season of birth. Also, a Duncan's multiple range test was performed. Results and conclusions: CHSE showed low productive parameters that were mostly affected by the variables sex and farm [p ≤ 0.05]. CHSs displayed a low to moderate productive performance and many traits were also affected by sex and farm [p ≤ 0.05]. Lastly, CHSP showed moderate to high productive parameters, which were mainly affected by parent, season, and type of birth [p ≤ 0.05]. The results determined the productive performance of the three sheep biotypes, among which CHSE showed low growth parameters, CHSS showed low to moderate parameters, and CHSP displayed moderate to high parameters. In all cases, the three biotypes were mostly affected by non-genetic variables.

89 Influence of Melatonin Supplementation in Pregnant Cattle Consuming Endophyte-Infected Tall Fescue Seed on Offspring Performance

Abstract The objective was to evaluate growth performance and estimates of body composition in offspring of dams that consumed diets containing tall fescue seed with (E+) or without (E-) the toxic endophyte and with or without melatonin during mid-late gestation. Pregnant heifers (n = 57) artificially inseminated with sex-sorted semen (X chromosome-bearing sperm) from a single Angus sire were administered dietary treatments in a 2 x 2 factorial treatment arrangement (E- without melatonin, E-/NM; E- with melatonin, E-/M; E+ without melatonin, E+/NM; or E+ with melatonin, E+/M; melatonin dose: 100 µg/kg of BW) for a 70-day period between May and July starting at 160±13 d of gestation to mimic ergot alkaloid concentrations in a grazing scenario. All diets contained corn gluten and molasses and were fed using SmartFeed Pro (C-Lock Inc.) controlled feeding units between 0900 and2 1200 h daily. Cattle were removed from dietary treatments 39 ± 19 d before calving. Two replicates were housed separately in an open-air barn, each with a 1.2-ha paddock. Prior to and following the 70-d treatment period, all cattle were maintained as a single group free from toxic fescue. Calves were weaned at 226 ± 19 d of age. Gestation length, calf birth weight, 205-day adjusted weaning weight (205-d WW), carcass ultrasonography measures (ribeye area, REA; REA/CWT; percent intramuscular fat, IMF; rib fat thickness, UFAT; rump fat thickness, URUMP), post-weaning weights (recorded every 28 d between weaning and 84 d post-weaning), and post-weaning ADG (between weaning and 84 d post-weaning) were evaluated in offspring (n = 44). Post-weaning calf weights were analyzed using the MIXED procedure of SAS specific for repeated measures with treatment and time as fixed effects and replicate as random. All other variables were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and replicate as random with gestation length as a covariate for birth weight. Gestation length, birth weight, 205-d WW, and post-weaning calf weight were decreased (P &amp;lt; 0.04) in offspring of dams that consumed E+ relative to E- during gestation. Birth weight was increased (P = 0.02) in offspring of dams receiving melatonin relative to those without melatonin during gestation. The 205-d WW and REA were decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P &amp;lt; 0.03). Post-weaning weight tended to be decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P = 0.06). The UFAT tended to be decreased (P = 0.06) in offspring of dams that consumed E+ relative to E- during gestation. There were no other effects of treatment, time or the interaction (P &amp;gt; 0.10). To our knowledge, these preliminary results are the first to evaluate the potential of melatonin as a therapeutic to recover performance losses in offspring born to pregnant cattle consuming toxic fescue.

47 Influence of Melatonin Supplementation in Pregnant Cattle Consuming Endophyte-Infected Tall Fescue Seed on Offspring Performance

Abstract The objective was to evaluate growth performance and estimates of body composition in offspring of dams that consumed diets containing tall fescue seed with (E+) or without (E-) the toxic endophyte and with or without melatonin during mid-late gestation. Pregnant heifers (n = 57) artificially inseminated with sex-sorted semen (X chromosome-bearing sperm) from a single Angus sire were administered dietary treatments in a 2 x 2 factorial treatment arrangement (E- without melatonin, E-/NM; E- with melatonin, E-/M; E+ without melatonin, E+/NM; or E+ with melatonin, E+/M; melatonin dose: 100 µg/kg of BW) for a 70-d period between May and July starting at 160 ± 13 days of gestation to mimic ergot alkaloid concentrations in a grazing scenario. All diets contained corn gluten and molasses and were fed using SmartFeed Pro (C-Lock Inc.) controlled feeding units between 0900 and 1400 h daily. Cattle were removed from dietary treatments 39 ± 19 days before calving. Two replicates were housed separately in an open-air barn, each with a 1.2-ha paddock. before and following the 70-d treatment period, all cattle were maintained as a single group free from toxic fescue. Calves were weaned at 226 ± 19 d of age. Gestation length, calf birth weight, 205-day adjusted weaning weight (205-d WW), carcass ultrasonography measures (ribeye area, REA; REA/CWT; percent intramuscular fat, IMF; rib fat thickness, UFAT; rump fat thickness, URUMP), post-weaning weights (recorded every 28 days between weaning and 84 days post-weaning), and post-weaning ADG (between weaning and 84 days post-weaning) were evaluated in offspring (n = 44). Post-weaning calf weights were analyzed using the MIXED procedure of SAS specific for repeated measures with treatment and time as fixed effects and replicate as random. All other variables were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and replicate as random with gestation length as a covariate for birth weight. Gestation length, birth weight, 205-d WW, and post-weaning calf weight were decreased (P &amp;lt; 0.04) in offspring of dams that consumed E+ relative to E- during gestation. Birth weight was increased (P = 0.02) in offspring of dams receiving melatonin relative to those without melatonin during gestation. The 205-d WW and REA were decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P &amp;lt; 0.03). Post-weaning weight tended to be decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P = 0.06). UFAT tended to be decreased (P = 0.06) in offspring of dams that consumed E+ relative to E- during gestation. There were no other effects of treatment, time or the interaction (P &amp;gt; 0.10). To our knowledge, these preliminary results are the first to evaluate the potential of melatonin as a therapeutic to recover performance losses in offspring born to pregnant cattle consuming toxic fescue.

155 Rams Enrolled in the National Sheep Improvement Program have Improved Performance and Value in Ram Test Program

Abstract Genetic evaluation programs can provide valuable selection tools for sheep breeders. However, industry acceptance and utilization of these tools is still limited. The objective here was to evaluate the performance and value of rams enrolled in the National Sheep Improvement Program (NSIP) compared with those not enrolled during a ram test program. Rams (Katahdin = 16, Texel = 3) were delivered to the Southwest Virginia Agricultural Research and Extension Center Ram Test on May 31. Rams were dewormed and rested for two weeks. On June 21, rams were given Haemonchus contortus L3 larvae adjusted for body weight (average = 5000 L3). FAMACHA scores and fecal egg counts (FEC) were monitored every two weeks until August 30. Rams were dewormed based on FAMACHA ≥ 3. The top 50% of rams, excluding any dewormed rams, based on the sale index [Sale Index = 0.50*(0.33*average daily gain ratio + 0.67*weight per day of age ratio) + 0.50*logFEC ratio] were sold at auction as breeding stock. Rams were classified as NSIP if enrolled. Statistical analyses were performed using SAS (SAS Institute, Cary, NC). Of the19 rams on test, 52% were NSIP. Thirteen rams required deworming during the test (38% of these were NSIP rams). Average sale index of NSIP rams tended to be greater than that of non-NSIP rams (101.4 vs. 98.3, P = 0.06). Of rams with sale index ≥ 100 (top 50%), a greater percentage of these rams were NSIP vs. non-NSIP (61% vs. 39%, respectively; P &amp;lt; 0.05). When NSIP status was evaluated for the top 20% of rams (sale index ≥07), a greater percentage of these rams were also NSIP vs. non-NSIP (78% vs. 22%, respectively; P &amp;lt; 0.01). Rams (n = 57) were sold on September 23 with an average sale price of $1,482. Rams enrolled in NSIP commanded greater prices than those not enrolled ($1,659 vs. $1,222, P &amp;lt; 0.05). When sale price was regressed on sale index for NSIP and non-NSIP rams, R2 for NSIP rams was 0.19 compared with the R2 for non-NSIP rams of 0.76. Given the weaker relationship between price and sale index for NSIP rams, estimated breeding values (EBVs) were evaluated. NSIP rams with EBVs reported for post-weaning weight, post-weaning FEC, and Maternal Hair Index sold for greater prices than those rams missing one or all of these EBVs ($1,837 vs. $971, respectively; P &amp;lt; 0.05). In summary, NSIP rams had greater performance (as indicated by sale index) and value compared with non-NSIP rams. For rams enrolled in NSIP, sale index was a poor predictor of value indicating buyers may be considering other factors besides sale index, such as EBVs, when purchasing NSIP rams.

Genetic parameters for mouth size and their influence on growth traits in pasture-raised Nelore cattle.

Evaluating traits that allow breeders to increase production efficiency in beef production systems is important. The mouth size score is a trait easily measured and implemented by breeders. Bite size is related to mouth size in beef cattle and is a determinant of daily feed intake of pasture-raised animals, influencing their growth. The aim of this study was to estimate genetic parameters for mouth size (MS), weaning weight (WW) and postweaning weight gain (PWG) of Nelore cattle and to evaluate the influence of the interaction between MS and WW on PWG. Phenotypic records of 134,282 Nelore animals born between 1995 and 2019 were used. Variance components were estimated using multi-trait animal model with the Bayesian method. The model included the contemporary group as fixed effect, age at measurement of the trait as linear covariate, and direct additive genetic and residual effects as random effects. For WW, random maternal and maternal permanent environmental effects were added to the model. A Bayesian approach was used to analyze the interaction between WW clusters and MS. The heritability estimates were 0.24, 0.15 and 0.23 for MS, WW and PWG, respectively. The genetic correlation between variables studied ranged from 0.24 to 0.46. The results suggest that animals with a larger mouth tend to have greater PWG, demonstrating the positive influence of MS score on the postweaning performance of cattle. The direct heritability estimates confirm the possibility of selecting animals for the traits studied.

Multiple‐trait and structural equation modelling approaches to infer genetic relationships between tail length and weight traits in Merinoland sheep

Tail docking is routinely conducted in long-tailed sheep breeds to prevent flystrike infections, but it is not in agreement with legal guidelines and animal welfare issues. Selection on short tails is a sustainable alternative in this regard, but side effects on other breeding goal traits are unclear. In consequence, the present study aimed to estimate genetic parameters for tail length (TL) at birth, birth weight (BW), weaning weight (WW) and postweaning weight (PWW) at the slaughtering date considering single-trait (STM), multiple-trait (MTM) and structural equation models (SEM) with different random effects, and accordingly, different covariance structures. The SEM considered time-lagged recursive relationships among response variables in three different pathways. The first path pertained to the effect of TL on WW and of WW on PWW. The second path reflected the effect of BW on WW and of WW on PWW. The third path was the recursive effect of TL on PWW. The phenotypic data consisted of 2803 records for TL, 13,042 records for BW, 1556 records for WW and 3986 records for PWW from Merinoland lambs. Lambs were born in the period from 1995 to 2021 and kept at the university Gießen research station, Germany, with their naturally long tails. Genetic statistical model evaluation based on Bayesian and Akaike's information criteria suggested models simultaneously considering direct genetic, maternal genetic and maternal permanent environmental effects and respective covariances. For statistical models including the same random effects and covariance structures, SEM were superior over MTM. The direct heritability for TL from the best-fitting STM was 0.60 ± 0.08, indicating the potential for genetic reduction of tail length within a few generations. For growth traits, the direct heritabilities ranged from 0.16 ± 0.03 for BW to 0.31 ± 0.09 for PWW. The maternal heritabilities were 0.03 ± 0.03 for TL, 0.12 ± 0.02 for BW, 0.04 ± 0.03 for WW and 0.07 ± 0.03 for PWW, reflecting small, but the non-significant influence of uterine characteristics on the tail development. The direct genetic correlations between TL and all weight traits were positive and very similar to MTM and SEM but reflected antagonistic genetic relationships from a breeding perspective. Oppositely, the structural equation coefficients reflecting trait associations phenotypically were negative (favourable) for the time-lagged effects of TL on WW and on PWW. As an explanation, lambs with long and woolly tails have an increased risk for contamination with dirt and dust causing infections, which in turn impairs the body weight development. In conclusion, breeding on short tails should consider trait-associated environmental risk factors, for example, disease susceptibility, which can be mimicked via SEM approaches.

SNP- and haplotype-based single-step genomic predictions for body weight, wool, and reproductive traits in North American Rambouillet sheep.

Rambouillet sheep are commonly raised in extensive grazing systems in the US, mainly for wool and meat production. Genomic evaluations in US sheep breeds, including Rambouillet, are still incipient. Therefore, we aimed to evaluate the feasibility of performing genomic prediction of breeding values for various traits in Rambouillet sheep based on single nucleotide polymorphisms (SNP) or haplotypes (fitted as pseudo-SNP) under a single-step GBLUP approach. A total of 28,834 records for birth weight (BWT), 23,306 for postweaning weight (PWT), 5,832 for yearling weight (YWT), 9,880 for yearling fibre diameter (YFD), 11,872 for yearling greasy fleece weight (YGFW), and 15,984 for number of lambs born (NLB) were used in this study. Seven hundred forty-one individuals were genotyped using a moderate (50 K; n=677) or high (600 K; n=64) density SNP panel, in which 32 K SNP in common between the two SNP panels (after genotypic quality control) were used for further analyses. Single-step genomic predictions using SNP (H-BLUP) or haplotypes (HAP-BLUP) from blocks with different linkage disequilibrium (LD) thresholds (0.15, 0.35, 0.50, 0.65, and 0.80) were evaluated. We also considered different blending parameters when constructing the genomic relationship matrix used to predict the genomic-enhanced estimated breeding values (GEBV), with alpha equal to 0.95 or 0.50. The GEBV were compared to the estimated breeding values (EBV) obtained from traditional pedigree-based evaluations (A-BLUP). The mean theoretical accuracy ranged from 0.499 (A-BLUP for PWT) to 0.795 (HAP-BLUP using haplotypes from blocks with LD threshold of 0.35 and alpha equal to 0.95 for YFD). The prediction accuracies ranged from 0.143 (A-BLUP for PWT) to 0.330 (A-BLUP for YGFW) while the prediction bias ranged from -0.104 (H-BLUP for PWT) to 0.087 (HAP-BLUP using haplotypes from blocks with LD threshold of 0.15 and alpha equal to 0.95 for YGFW). The GEBV dispersion ranged from 0.428 (A-BLUP for PWT) to 1.035 (A-BLUP for YGFW). Similar results were observed for H-BLUP or HAP-BLUP, independently of the LD threshold to create the haplotypes, alpha value, or trait analysed. Using genomic information (fitting individual SNP or haplotypes) provided similar or higher prediction and theoretical accuracies and reduced the dispersion of the GEBV for body weight, wool, and reproductive traits in Rambouillet sheep. However, there were no clear improvements in the prediction bias when compared to pedigree-based predictions. The next step will be to enlarge the training populations for this breed to increase the benefits of genomic predictions.

PSI-5 Relationships of Feed Efficiency and Growth Estimated Breeding Values in Range Sheep

Abstract United States sheep producers have selected range sheep for larger post-weaning weights through estimated breeding values (EBVs) for the past forty years. This has led to producers perceiving more feed being required than historical averages. Therefore, the objective of this study was to quantify the relationship between lamb growth estimated breeding values, feed intake, and feed efficiency. Eighty ewe lambs (40 Targhee and 40 Rambouillet) were weaned at four months of age and put onto a GrowsafeTM feeding system for a 42-day feeding trial with a 14-day adaption period. Ewe lambs were weighed weekly and at the beginning and end of the trial. Body weights, average daily gain (ADG), and daily feed intake measurements were used to calculate Residual Feed Intake (RFI). The ewe lambs’ post-weaning weight EBV was associated to feed intake, mid-trial metabolic body weight, and RFI. These experimental procedures were repeated in a second trial when the same ewes were yearlings and at maintenance. While post-weaning weight EBVs were predictive to dry matter intake (P &amp;lt; 0.05), there was no relationship between post-weaning weight EBVs and RFI (P &amp;gt; 0.05), this association was constant across both trials. A ewe’s post-weaning weight EBV was also predictive of mid-trial body weight in both trials (P &amp;lt; 0.05). This suggests that while selection for higher post-weaning weight animals may increase sheep producers’ feed usage due to larger body size, feed efficiency is not associated with the post-weaning weight EBV. To investigate if the RFI measurements from the growth stage are predictive of maintenance requirements, we further compared the RFI, ADG, mid-trial body weights, and DMI measurements between the two trials. Growth RFI measurements were found not to be predictive of RFI in maintenance. Therefore, caution should be used when utilizing RFI from the growth phase as an indicator for feed efficiency in maintenance. Alternatively, we found that DMI from the growth stage was predictive of DMI of the maintenance stage (P &amp;lt; 0.05). Ewes’ mid-trial body weight in the first trial was also predictive of the mid-trial body weight of the second trial (P &amp;lt; 0.05). Mid-trial body weight was positively associated with DMI in both trials (P &amp;lt; 0.05). Thus, the differences in ewe body weight were likely driving the differences seen in dry matter intake. Overall, our results suggest that range producer’s selection towards sheep with larger post weaning weight EBVs may be increasing ewe DMI due to increased body size but is not negatively affecting the ewe’s overall feed efficiency.

Characterizing the vaginal microbiota of high and low producing Poll Merino and White Suffolk ewes.

There is a substantial, and growing, body of research focused on manipulating gastrointestinal microbes to affect health and production. However, the maternal vaginal microbiota and its effects on neonatal inoculation and lifetime production have received little attention. We aimed to characterize the vaginal microbes of domesticated sheep to determine whether they differ across sheep breeds with differing meat and wool growth potentials and to determine a link between vaginal microbes and high and low producing animals. A flock of White Suffolk (n = 136) and Poll Merino (n = 210) ewes were sorted by the Australian Sheep Breeding Values (ASBV), for yearling fleece weight in the Merino and by post-weaning weight in the Suffolk ewes. The top and bottom ASBV sheep were selected for sampling and the resulting treatment groups were; High Suffolk (n = 12), Low Suffolk (n = 12), High Merino (n = 12), and Low Merino (n = 12) ewes. A double guarded culture swab was used to sample from the surface of the vaginal epithelium. Diversity profiling analysis of vaginal bacterial communities was conducted using 16S rRNA amplicon sequencing. Breed and ASBV group differences in bacterial communities were tested. Within breed, there were no significant differences in ewe vaginal bacterial communities associated with ewe production parameters; however, there was a significant difference in ewe vaginal bacterial communities between breeds. We have been able to characterize the normal vaginal microbiota of nonpregnant ewes and demonstrate a rich microbial community.