The purpose of study to evaluate the effectiveness of melatonin implants and progesterone hormone as non-surgical methods for controlling reproductive activity in adult male cats. Twenty-four healthy toms, aged 3–4 years, were equally divided into three groups: a control group, a melatonin-treated group (18mg S.C.) and progesterone-treated group (megestrol acetate 2.5 mg every 10 days for two months). All cats were housed in comparable environmental conditions, and behavior observations as well as serum testosterone concentrations were taken 20, 40 and 60 days after treatment. melatonin implants and progesterone hormone both led to testicular regression (p <0.05) of treated tom cats comparative to control. Testicular length and width, scrotal circumference, seminiferous tubule diameter, interstitial tissue thickness, number of interstitial cells, and height of germinal epithelium all showed a gradual decrease over the course of 60 days. Regression was modest with melatonin (MLT) and stronger and earlier with progesterone. By day 60, testicular length and width decreased to approximately 17 mm (MLT) and 14 mm (in P4-treated cats), while scrotal circumference was reduced to 2.44 cm (MLT) and 1.52 cm (P4-treated). Histologically, melatonin led to a gradual vacuolation and desquamation of germ cells, whereas progesterone induced marked seminiferous atrophy, change of spermatogenic cells and expansion of the interstitium. There were no local or systemic adverse reactions. Results indicate that both have an inhibitory effect on testicular structure and reproductive activity, the suppression being reversible and progesterone having more potent inhibition.

Brazil is the largest beef exporter and has the largest commercial herd in the world, making it necessary to evaluate zebu breeds to promote their genetic improvement, as they make up a large part of the Brazilian beef herd. The sire plays a major role in the formation of elite and commercial herds. The aim of this study was to evaluate males of the Nellore, Nellore Mocho and Tabapuã breeds, allocated to categories 1 (8–9 months) to 17 (33–36 months), which were present in Expozebu between 2000 and 2019 in the city of Uberaba. Based on the animals’ body biometry data, the following traits were measured in Nellore, Nellore Mocho and Tabapuã males: weight (WE), forelimb height (FH), hindlimb height (HH), length (LE), thoracic perimeter (TP), scrotal circumference (SC), loin eye area (LEA), subcutaneous fat thickness (SFT), and subcutaneous fat thickness of the croup (SFC). Data were statistically analysed between breeds, and their correlations were determined. The Nellore males were superior to the Nellore Mocho and Tabapuã in terms of WE, FH, HH, and LE. As for TP and SC, the Nellore males were similar to the Tabapuã in most categories. In terms of carcass traits, Nellore males also had a higher LEA, STF, and STC in certain categories. There was a high correlation between WE and biometric traits, such as FH, HH, LE and TP, with TP having the highest correlation. The carcass traits showed the highest correlations with WE and TP, moderate to high correlations with biometric traits, and moderate values between them, except for LEA, which obtained high values with STF (0.80 for Nellore, 0.79 for Nellore Mocho and 0.76 for Tabapuã). The data presented on the performance of Nellore, Nellore Mocho and Tabapuã males at different ages can be used as a reference for assessing cattle development in preparation for shows and/or intensive meat production systems.

This study aimed to estimate the variance components, heritabilities and genetic correlations between four new different categories of stayability (STAY48-2, STAY48-3, STAY54-2, STAY54-3) with weight at 240 days of age (W240), weight at 450 days of age (W450), scrotal circumference at 365 days of age (SC365), age at puberty in males (APM), traditional stayability (STAY72), probability of precocious calving at 30 months of age (PPC30), ribeye area (REA), rump fat thickness (RFT), residual feed intake (RFI), dry-matter intake (DMI), residual live weight gain (RG) and frame score (FRAME). Records from 80,958 females born between 2000 and 2019, exposed to mating starting at 10 months of age, raised on pasture from 508 farms in the central-west, southeast, northeast and northern regions of Brazil that participate in the National Association of Breeders and Researchers (ANCP), were analysed. The (co)variance components were estimated by Bayesian inference in a two-trait animal model. The posterior means of heritability estimates for STAY48-2, STAY48-3, STAY54-2 and STAY54-3 were moderate to low, 0.20, 0.20, 0.22 and 0.22 respectively. The traits related to different categories of stayability showed low genetic correlations with male reproductive traits (-0.22 to 0.19), feed efficiency (-0.03 to 0.13), carcass (0.11 to 0.18) and body composition (-0.09 to -0.6), moderate with growth (0.04 to 0.29) and high with sexual precocity (0.88 to 0.93) and fertility (0.65 to 0.73). The heritability estimates of the different categories of stayability indicate genetic improvement for longevity in early challenged females. The genetic correlations with sexual precocity showed that its use as selection criteria is recommended for production systems of younger females challenged in the reproductive season rather than traditional stayability to increase the probability of stayability in the herd.

This study estimated genetic parameters for pregnancy loss (PL) in Brahman cattle and evaluated the genetic correlation of PL with growth and reproductive traits using both the pedigree relationship matrix (A) and pedigree plus genomic relationship matrix (H). Data were collected from two herds in Bolivia, focusing on three age groups: heifers, primiparous and multiparous cows. Threshold animal models were fitted to each group. Multitrait models were fitted between the PL at different age group and between PL and the following traits: adjusted weights at 450 (W450) and 550 (W550) days, scrotal circumference adjusted at 450 (SC450) and 550 (SC550) days, accumulated cow productivity (ACP), age at first calving (AFC) and stayability (STAY). The H matrix increased the heritability for PL in heifers from 0.06 to 0.11. The genetic correlation between PL in heifers and primiparous cows changed using H (from 0.18 to 0.7), and it was high between heifers and multiparous cows. Moderate-high negative genetic correlation was observed between PL and STAY, with changes in heifers when using H (-0.17 to -0.57). AFC and PL presented medium-high positive genetic correlations. Negative correlations between PL and SC450 or SC550 were found in primiparous and multiparous cows. Using H, the correlation between PL in heifers and ACP shifted from 0.08 to -0.31, showing medium-high negative correlations for the other two age groups. Genetic correlations were low between PL and W450 or W550. Genomic information allows the use of PL as a selection criterion in heifers. Selection for major sexual precocity, longevity and productivity would enable the reduction of pregnancy loss.

Simple SummaryReproduction plays a crucial role in the long-term sustainability of livestock, particularly in extensive production systems. However, reproductive traits typically exhibit low heritability, mainly due to the general lack of objective performance control criteria related to fertility in breeding females, and the fact that these traits are subject to numerous environmental effects that are difficult to quantify. This means that, in many beef cattle breeds, an indirect selection criterion is being used, such as the male’s scrotal circumference, because it is considered to be associated with the fertility of his daughters. This would imply the existence of genes with pleiotropic effects in both sexes. To better understand the genetic architecture underlying these traits, a genome-wide association study was conducted for scrotal circumference (SC) and several female fertility traits within the Retinta cattle breed. Genes previously reported in cattle breeds for SC and female fertility traits were identified in this study. Two of these main genes were detected in the GWAS of the bull’s scrotal circumference and parameters related to cow fertility.Fertility is key for calf production. Direct selection for female fertility under field conditions is hindered by low accuracy and selection response. An alternative widely implemented is selection for scrotal circumference (SC), genetically correlated with daughter fertility. This study performed a genome-wide association study (GWAS) to identify genomic regions and candidate loci linked to SC and female fertility in Retinta cattle. A multivariate ssGBLUP was applied using SC records from 1061 bulls, fertility-related traits from 59,254 females and genotypes from 1230 animals using the Axiom™ Bovine Genotyping v3 Array (65k). The ssGWAS revealed 23 1-Mb windows explaining >1% of additive genetic variance for SC, one on chromosome 2 and 22 on chromosome 3. Within these windows, 198 regions spanning 118 protein-coding genes and 80 RNA genes were identified. Several genes, including GSTM3, SPATA1, HFM1, and MSH4, were previously associated with male fertility. Six regions overlapped across male and female traits, containing two protein-coding genes (THSD7B and ENSBTAG00000021755). Identification of genomic markers linked to both female fertility and male SC enables selection of superior animals, improving reproductive efficiency and advancing knowledge of the genomic basis of male–female fertility relationships.

Abstract Two experiments were designed to evaluate including an omega-3 fatty acid-based supplement in the basal diet of developing bulls post-weaning. In both experiments, spring-born bull calves of either Angus, Simmental, or Hereford breeding were weaned in September and developed in an automated feed intake management system. Bulls were managed as common groups and individually fed from precision intake management bunks; thus individual bull was considered the experimental unit in both experiments. In experiment 1, in a completely randomized design, bulls (n = 42) were stratified by age and BW and randomly assigned to 1 of 3 treatments with 14 bulls per treatment: 0.0 (CON), 0.22 (MOD), or 0.43 (HI) kg per hd per day (DM basis) of an omega-3-based supplement added to a common corn silage and wet corn gluten feed-based growing diet. Dietary treatments began in December (352 ± 19 kg of initial BW; 292 ± 6.25 d of age) and were applied for approximately 60 d. Data were analyzed using the GLIMMIX procedure of SAS with significance declared at P ≤ 0.05. Initial age and BW were similar among treatments (P ≥ 0.98). Dry matter intake (DMI) did not differ (P = 0.64). Bulls on the HI treatment had greater (P ≤ 0.05) daily gain compared to CON and MOD, although ending BW and gain-to-feed ratio did not differ (P ≥ 0.52). Scrotal circumference (SC) and blood serum fatty acid levels were not influenced (P ≥ 0.67). In experiment 2, bulls (n = 41, 332 ± 14 kg of initial BW; 291 ± 6.25 d of age) received the same supplementation treatments for 80 days applied to an isonitrogenous corn silage and dried distillers grains based diet. No treatment differences were detected for final BW (P = 0.86), average daily gain (P = 0.49), and DMI (P = 0.39). Gain to feed tended to be different (P = 0.08), but SC was not impacted by dietary treatments (P = 0.84). Data suggest incorporating an omega-3 fatty acid based supplement into the basal diet for developing beef bulls improves daily gain without impacting dry matter intake, and scrotal circumference within the level and duration of supplementation in these experiments.

Abstract The objective of this study was to compare bull performance, carcass characteristics, and health metrics when using the SenseHub® Feedlot tag (SFT) vs conventional human walk through methods (CHM) to monitor bull health at a centralized bull test. SFT is an electronic ear tag that tracks animal activity and measures body temperature to signal when animals should be pulled for health treatment. Bulls on the pull list provided by SFT were evaluated and treated the same day. Bulls were pulled based on visual appraisal of the animal by farm staff for CHM. CHM Bulls (n = 40) arrived on October 3rd, 2023 in year 1 and SFT Bulls (n = 27) arrived on October 1st, 2024 in year 2. Breeds represented included: Angus, Simmental, Percentage Simmental, and Red Angus. Bulls were fed the same diet, in the same facility, and were given 21 d of accumulation before beginning a 90 d performance test. Bulls were weighed on two consecutive days and those weights were averaged to calculate start and end weights. Carcass measurements of actual backfat, adjusted intramuscular fat, and adjusted rib eye area were measured using ultrasound by the same technician on the 3rd Thursday in January. Scrotal circumference was measured the third Thursday in February utilizing the same veterinarian. Bull test performance metrics of ADG and weight per day of age (WDA) were calculated while actual birth weights and calving ease direct (CED) EPDs were obtained from the registered animal database. Health metrics including: number of times treated, mortality, and cost of treatment were recorded. Data were analyzed using the PROC GLIMMIX procedure of SAS with year and breed as covariates. Correlations were made using the PROC CORR procedure of SAS. Number of times treated increased (P = 0.04) 152% with SFT compared to CHM. As a result, cost of treatment in $ per head tended to increase (P = 0.20) $15.71 with SFT. ADG and scrotal circumference did not differ (P > 0.21). Actual birth weight did not differ (P = 0.27); however, WDA was 0.15 kg higher for SFT bulls. Carcass characteristics did not differ (P > 0.35). Mortality rate was 4.8% (P = 0.26) for CHM compared to 0% for SFT. Number of times treated tended to be correlated to scrotal circumference (r = 0.32; p = 0.07) and CED EPD (r = -0.27; p = 0.1). Overall, SFT bulls were treated more times and had higher WDA than CHM bulls therefor cost per head numerically increased and mortality rate numerically decreased for SFT bulls.

Abstract The objective of this study was to obtain (co)variance components, heritability, and genetic and phenotypic correlation estimates for enteric methane emission, residual feed intake, growth and carcass trait and reproductive indicators. Data from 146 feed efficiency trials with male and female Nellore cattle born between 2008 and 2023 from 146 herds in Central Brazil were analyzed. Trial data along with diet NDF content were used to estimate the methane emission intensity (g CH4/kg ADG) for each individual, using an equation developed by Medeiros et al., 2014: CH4 (g/d) = -0.1011 + 0.02062*DMI (kg/d) + 0.001648*NDF (% of DMI). Other data included pedigree information, body weight, carcass traits and reproductive indicator traits. Numbers of records varied from 3,869 (methane) to 42,840 (carcass data). Continuous traits were analyzed using a linear animal model. Two-trait analyses were performed using the restricted maximum likelihood to estimate the variance components, heritabilities and genetic and phenotypic correlations among traits. The estimated heritability of methane emissions was 0.117 ± 0.025. The genetic correlations of methane emissions with most performance and reproductive traits were low and not different from zero: BW at 240 d (0.019 ± 0.0003), BW at 450 d (0.022 ± 0.0003), ribeye area (-0.077 ± 0.098), rib fat (-0.020 ± 0.094), rump fat (0.091 ± 0.089), intramuscular fat % (-0.008 ±0.109), scrotal circumference (0.015 ± 0.0004), and age at first calving (0,072 ± 0,187), The same was true for early calving probability (-0,139; -0,384, 0,106) and stayability (-0,079; -0,324, 0,166) (means and highest posterior density intervals). Exceptions were the moderate genetic correlations of methane emissions with DM intake (0.486 ± 0.018) and the high correlation of methane with residual feed intake (RFI; 0.808 ±0.015). Thus, selection to improve weaning and yearling weights and carcass traits would not affect methane emissions. Genetic selection to reduce methane emissions is feasible and would also reduce DMI and RFI. Conversely, selection to improve RFI can be used to identify animals with lower methane emissions. Medeiros, S. R, L. G. Barioni, A. Berndt, M. C. Freua, T. Z. Albertini, C. Costa Jr., and G. B. Feltrin (2014) Modeling enteric methane emission from beef cattle in Brazil: A proposed equation performed by principal component analyses and mixed modeling multiple regression. Anais, Livestock, Climate Change and Food Security Conference, Madrid.

Abstract Inbreeding depression, defined as the reduction in mean performance due to increased homozygosity, has been extensively studied across various livestock species. With the advent of genomic information, inbreeding estimation has evolved beyond pedigree-based calculations to incorporate more precise genomic-based metrics. This study aimed to: 1) assess six different inbreeding metrics in Brazilian Angus cattle, using both pedigree and genomic information; and 2) estimate the impact of inbreeding depression on 12 traits currently evaluated by the Brazilian Angus Association. A dataset comprising 13,777 Brazilian Angus cattle genotypes imputed to the density of 78,837 markers was made available for this study. Phenotypic data included birth weight, weaning weight gain, post-weaning weight gain, yearling conformation, hair coat scores, scrotal circumference, ribeye area, back fat thickness, rump fat thickness, intramuscular fat, and tick count. Inbreeding coefficients were calculated using pedigree-based (entire population – FPEDtotal; genotyped individuals – FPEDgen), and genomic-based (genotype additive variance - FGRM, homozygous genotypes 1 - FHOM1, homozygous genotypes 2 - FHOM2, correlation between uniting gametes - FUNI, and runs of homozygosity - ROH) methods. Inbreeding depression was estimated using single-trait linear models, regressing phenotypic traits on inbreeding coefficients. Inbreeding coefficients ranged from -0.33 to 0.71 across different metrics, with the lowest mean values observed for FPEDtotal, FPEDgen, FGRM, FHOM1, FHOM2, FUNI, and ROH < 2Mb (all = 0.01), while the highest mean value was observed for FROH (0.13 ± 0.03). Correlations among inbreeding metrics varied from weak (-0.26; between FGRM and ROH 2-4Mb) to strong (0.97; between FROH and FHOM2), with pedigree-based inbreeding showing weak correlations with genomic-based metrics overall. The estimation of inbreeding depression revealed predominantly unfavorable effects, with the most pronounced impact observed for rump fat thickness, where a 1% increase in inbreeding (F8-16Mb) led to a 1.13% phenotypic reduction. However, increased effects were noted for intramuscular fat (FHOM2) and birth weight (F2Mb), with the latter rising by up to 0.83%. Additionally, birth weight exhibited differential responses based on ROH length, with shorter ROHs (F2Mb) increasing the effect, whereas longer ROHs (F8-16Mb) decreasing the effects. These findings highlight the complexity of inbreeding depression, emphasizing the importance of considering both the length and historical depth of inbreeding when assessing its impact on economically relevant traits.

Abstract This study was designed to evaluate the effects of including an omega-3 fatty acid-based supplement in the diet of developing beef bulls on biological parameters and fertility. Weaned beef bull calves (n = 39) of Angus, Hereford, or Simmental breeding were stratified by BW and age to one of three dietary treatments in a completely randomized design. Treatments consisted of including an omega-3-based supplement at 1 of 3 levels to a common corn silage-based growing diet in which all diets were formulated to be isonitrogenous. The levels of the omega-3 fatty acid-based supplement consisted of 0.00 (CON), 0.22 (MOD), 0.43 (HI) kg per hd per day (DM basis) and bulls (n = 13 per treatment) were managed as a common group and individually fed in precision intake management bunks with individual bull as the experimental unit. Bulls were supplemented for 80 days starting in late November of 2024 ending in early February 2025 with an average ambient temperature of –0.5 °C. Ration samples were collected weekly. Blood samples were collected on D0, D57, and D80 by coccygeal venipuncture. Three day shrunk body weights were collected and averaged for D0 and D80 with a single day weight on D57. Testicular thermal images were taken on D0 and D80, and breeding soundness exams were performed by trained technicians on D57, D80 and D101. At the end of the supplementation period on D80, bulls in the HI treatment group had a greater (P < 0.01) percentage of morphologically normal sperm cells in the ejaculate than CON, while the MOD bulls had a tendency (P = 0.06) for improved morphology compared to bulls not supplemented with an omega-3 fatty acid-based supplement. Supplementation (P < 0.01) and breed (P < 0.01) had a significant effect on morphology. Breed and age had a significant effect (P < 0.01), while supplementation and BW had a significant effect (P < 0.05) on D80 motility. Scrotal circumference was not impacted (P > 0.05) by breed or supplementation. Age and weight were significant for scrotal circumference at day 80 (P < 0.05). Bulls supplemented with an omega-3 fatty acid based supplement had greater morphology and motility than non-supplemented bulls. Data suggest that dietary incorporation of an omega-3 fatty acid based supplement into the basal diet of young developing beef bulls may influence semen quality parameters under dietary levels and duration of feeding observed in this experiment.

Abstract Due to their significant economic impact, reproductive traits are crucial in beef cattle breeding programs. However, identifying the genomic regions associated with these traits requires large datasets to capture the complex genetic architecture underlying their variability. Traits such as age at first calving (AFC), stayability (STAY), and scrotal circumference measured at 365 and 450 days (SC365 and SC450, respectively) are highly polygenic, making it essential to leverage robust genomic methodologies to uncover meaningful associations. In this study we aimed to identify candidate genes and genomic regions associated with reproductive traits in Nellore cattle. A dataset containing genomic estimated breeding values (GEBVs) for 304,782 Nellore animals genotyped with 437,650 SNPs (after quality control) was made available by the Brazilian Association of Zebu Breeders (ABCZ). The Algorithm for Proven and Young (APY), implemented in the PREGSF90 software, was used to compute the matrix using 36,000 core animals. Subsequently, the SNP solutions were estimated by back-solving the GEBVs predicted by ABCZ using the single-step GBLUP method. We identified genomic regions associated with these traits using sliding windows of 175 consecutive SNPs, and the top 1% of genomic windows were used to annotate positional candidate genes. The top 1% genomic windows for these traits explained between 2.8% (STAY) to 3.0% (AFC) of the additive genetic variance, highlighting their polygenic nature. Functional analysis of the candidate genes within these genomic regions provided valuable insights into the genetic architecture underlying reproductive traits in Nellore cattle. For instance, our results revealed genes with important functions for each trait, such as SERPINA14 (plays a key role for the endometrial epithelium) and CCNB1 (essential for spindle checkpoint regulation, meiosis, and mitosis) identified for AFC. ARHGAP18 (involved in maintaining endothelial cell alignments) and KCNC1 (regulates potassium ion flow crucial for animal longevity) were identified for STAY. Additionally, genes such as EVI5 (important for centrosome stability), BRDT (essential for male germ cell differentiation), KIT (associated with the male germ cells), and (involved in spermatogenesis and intraflagellar transport) were identified for both SC365 and SC450. We identified genomic regions and candidate genes, some of which have been previously reported in the literature, while others are novel discoveries that warrant further investigation. These findings contribute to gene prioritization efforts, facilitating the identification of functional candidate genes that can enhance genomic selection strategies for economically important traits in Nellore cattle.

Abstract Overnutrition in young beef bulls has been previously reported to negatively impact semen quality during industry-standard breeding soundness examinations. The objective of the present study was to characterize the metabolic and endocrine profile of young bulls exposed to divergent planes of nutrition. Half-siblings Angus yearling bulls (n = 44) were utilized in a completely randomized design. Bulls were stratified by age, body weight (BW), and body condition scores (BCS) before being randomly assigned 1 of 2 dietary treatments for 114 days: 1) Moderate Gain (MG): diet formulated to promote an average daily gain of 1.2 kg/d, or 2) High Gain (HG): diet formulated to promote an average daily gain of 1.8 kg/d. Throughout the study, bulls were housed in a feedlot facility equipped with a Smartfeed Pro automated bunk system that allowed for individual feed intake assessments daily. Body weight, BCS, and blood samples were collected on days 0, 38, 76, and 114. Changes in body composition were estimated using carcass ultrasonography on the same days. Average daily gain (P < 0.01) and dry matter intake (P < 0.01) were greater in HG compared with MG bulls. Moreover, HG bulls had decreased feed to gain ratio compared with MG bulls. Body weight, BCS, subcutaneous backfat, and intramuscular fat were greater (P ≤ 0.01) at the end of the feeding period in HG compared with MG bulls (treatment × day; P ≤ 0.04). Similar results were observed for circulating concentrations of glucose, insulin, leptin, cholesterol, and low-density lipoproteins (treatment × day; P ≤ 0.01). Bulls exposed to the HG diet also had decreased (treatment × day; P ≤ 0.02) circulating concentrations of non-esterified fatty acids and beta-hydroxybutyrate at the end of the feeding period compared with MG bulls. Insulin:glucose ratio and HOMA-IR, which are estimates of insulin resistance, were increased in HG compared with MG bulls at the end of the feeding period (treatment × day; P < 0.01). Moreover, HG bulls had greater (P = 0.02) circulating concentrations of haptoglobin at the end of the feeding period compared with MG bulls. Scrotal circumference tended (P = 0.10) to be greater at the end of the feeding period in HG compared with MG bulls; however, scrotal skin thickness and paired-testicular volume were similar (P ≥ 0.18) among treatments. In summary, the HG dietary treatment utilized in this study promoted an obese-like metabolic profile along with increased insulin resistance and systemic inflammation compared with the MG diet.

Abstract The microbiome in bull semen remains largely underexplored, particularly in relation to fertility metrics. This study aimed to characterize the seminal microbiome by integrating a comprehensive panel of flow cytometry assays along with the traditional breeding soundness exam (BSE) measurements. Two ejaculates at the BSE were collected via electroejaculation from yearling virgin beef bulls (n = 32). Microbiome samples from each ejaculate were used for 16s rRNA analysis. Flow cytometry (FC) assays for oxidative stress, DNA integrity, mitochondria membrane potential, viability, acrosome integrity, and capacitation status were performed on the ejaculate with the greatest progressive motility. Spermatozoa were incubated, after which motility, viability, capacitation status, and acrosome integrity were evaluated again. Alpha diversity increased with fertility across multiple categories. Most notably, bulls with greater mitochondrial membrane potential exhibited greater (P < 0.01) Shannon diversity. Similarly, bulls classified as fertile based on spermatozoa progressive and total motility were positively associated with microbial richness, Faith’s phylogenetic diversity, and Shannon diversity (P < 0.05). Evenness was positively associated with acrosome integrity at both FC evaluations (P < 0.02). Sire of bulls had an association to all alpha and beta diversity metrics (P < 0.01), suggesting a potential role of seminal microbiome transmission from sire to offspring. Microbiome between ejaculates differed (P < 0.03) when compared on a per bull basis, but did not differ (P >0.13) for the whole population. This suggests the first ejaculate removes microorganisms from the reproductive tract but does not change the overall composition of the microbiome in the population. Bray-Curtis distances were positively correlated (P < 0.04) with the abnormal morphology classifications of distal midpiece reflex, bowed midpiece, and bent principle piece, but there were no correlations (P > 0.13) with normal morphology. Additionally, Bray-Curtis had a positive relationship with acrosome integrity markers of dead disrupted, total disrupted, and total intact at both FC evaluations (P < 0.04). Limited number of taxa were identified as potential biomarkers, but bulls with greater scrotal circumference had enriched species, such as Canibacter oris, present (P < 0.02). We conclude that relationships exist between the seminal microbiome and fertility measures of the BSE and spermatozoa functional measures assessed via FC, but additional data is needed to understand any causal effects or potential biomarkers of microbial populations on bull field fertility.

Beyond the scrotal circumference: Exploring phenotypic, nutritional and metabolic traits associated with early sexual development in young Nelore (Bos indicus) bulls.

Breed-specific testicular ultrasound profiles and pubertal markers in Bos indicus and composite bulls.

BackgroundThe advent of next-generation sequencing enables the opportunity to use denser marker tools, up to whole-genome sequences (WGS), for genomic prediction in livestock. Improvement in genomic prediction (GP) accuracy from using WGS has been observed in simulation studies. In contrast, such advantage has found to be inconsistent once implemented in practice. The benefit of WGS appears to be from markers that are significant for the trait of interest. Thus, the main objective of this study was to investigate the predictive ability of adding preselected markers to the standard-industry 50k genotype for GP of economically important traits in Angus cattle, namely, birth weight (BW), scrotal circumference (SC), carcass weight (CWT) and carcass intramuscular fat (CIMF). Animals were genotyped with either commercial or customised SNP-genotyping arrays; then, the genotypes were imputed to WGS. The 50k genotype was used as the control group. Informative markers associated with the desired traits were extracted from WGS, then were added to the 50k genotype. Several methods were chosen to select different sets of informative markers, including LD-based pruning, top SNP from a genome-wide association study (GWAS), functional annotation based on Gene Ontology, cattle QTL database, and sequence annotation. In total, eight different sets of genotypes were investigated. We applied different statistical models to predict genomic breeding values, including GBLUP, BayesR, and BayesRC, and two-GRM GBLUP constructed separately from the 50k and the preselected genotype set.ResultsHeritability (h2) estimates were similarly calculated using different sets of genotypes and statistical methods across all traits. The log-likelihood ratio values revealed that two-GRM GBLUP was more suitable than the single-GRM GBLUP. There was no significant difference in accuracy and bias among the different sets of genotypes compared to the control group or the statistical methods, except for BW. For BW, the Bayesian models slightly outperformed GBLUP.ConclusionsThe findings suggest that potential improvements may be achieved by using preselected SNPs from the GWAS, a method that has proven within the population. The performance of preselected markers on GP influenced by several factors, including population structure, method used to select significant markers, and genetic architecture of traits.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12711-025-00999-7.

Reproductive performance depends on the adaptability of animals to climatic conditions. Holstein cattle are distributed throughout the world, but their reproductive efficiency can be impacted by the environment to which they are subjected. This study aimed to evaluate the growth of scrotal circumference (SC), seminal parameters and their correlation with genomic predictions of fertility in young Holstein bulls (n=102) raised in the Brazilian semiarid region. The study was developed at the São Bento do Una/IPA Experimental Station, located at GPS coordinates 83° 16’ 18” South latitude and 36° 27’ 59” longitude, altitude 625m and average THI of 69.21. The animals were evaluated from 12 to 24 months of age and were kept in a semi-confinement system. From 12 months of age, the animals underwent monthly PE measurement and semen collection for immediate analysis. To evaluate the correlation of subjective seminal parameters and the CASA system with genomic predictions, it was necessary to distribute the bulls into two groups (TG1 and TG2) according to the genotype, being TG1 (n=03 IPA genotype and TG2 (n=03 IPA x Imported genotype). The genomic evaluation was performed using the Clarifide® profile, using: Fertility Index (FI); Daughter Pregnancy Rate (TPF); Heifer Conception Rate (TCN) and Cow Conception Rate (TCV). The data were submitted to ANOVA, regression analysis and F test at 5%. Regarding PE, mean values were 31.40±0.27 cm, 38.40±0.11 cm and 42.24±0.11 cm at 12, 18 and 24 months (p<0.05). The mean sperm concentrations were 324 x 106, 727 x 106 and 1056 x 106 sperm/mL (p<0.05) at 12, 18 and 24 months, respectively. Seminal motility and morphology in CASA showed 59.9% and 63.5% of CM, 40.5% and 42.0% of CP and 57.7% and 62.1% of CN, respectively for TG1 and TG2. Regarding genomic predictions, only TCV was superior (p<0.05), in TG2, being 0.23. The Normal Cells phenotype presented correlation r=0.7994, r=0.6228 and r+0.7512 with TPF, TCV and IF, respectively. Therefore, it is concluded that young Holstein bulls raised in the semiarid present a PE growth curve and seminal parameters compatible with the desirable fertility estimate. However, only the seminal parameter CN showed a strong correlation with the genomic predictions of TPF, TCV and IF, regardless of the experimental group TG1 and TG2.

The objectives of this study were to model the relationship of PAP scores with production, maternal, and carcass (EPDs). Bull PAP scores were collected from 12-18-month-old Angus bull from a Montana-based Angus operation (>1600 m elevation, 5400 yearlings/18-month-old bulls from 2016-2023). Bulls with greater calving ease direct had lower PAP scores (p < 0.01; conditional r2 = 1.06%; marginal r2 = 0.62%). Bulls with greater birth weight EPDs had greater PAP scores (p < 0.01; conditional r2 = 1.15%; marginal r2 = 0.73%). Pulmonary arterial pressure was greater for bulls that had greater weaning weight EPDs (p < 0.01; conditional r2 = 0.82%; marginal r2 = 0.16%) and for bulls that had greater yearling weight EPDs (p < 0.01; conditional r2 =0.93%; marginal r2 = 0.24%). Bulls with greater PAP had greater carcass weight EPDs (p = 0.03; conditional r2 = 0.69%; marginal r2 = 0.18%). There were no observed relationships (p ≥ 0.17) between bull PAP and scrotal circumference, maternal milk, ribeye area, or marbling EPDs. In summary, PAP was related to calving ease direct, birth weight, weaning weight, yearling weight, and carcass weight EPDs. However, these relationships explain very little of the variation of PAP scores.

ABSTRACTIndirect predictions (IP) are used for young genotyped animals that lack phenotypes (of their own or from progeny) or are from commercial herds. The former can be left behind because they do not contribute to the official genomic evaluations. The latter are often excluded from the evaluations because they are not registered and may not have pedigree information. Including such animals could result in inflated and biased genomic breeding values (GEBV). In Brazil, pedigree, phenotype and genotype information is scarce for important breeds like Brahman, Guzerat, and Tabapua, while the Nellore breed has a substantial amount of information. IP for young animals of these breeds based on a larger reference population could enhance genomic selection accuracy. Our objective in this study was to compute IP for young genotyped Nellore, Brahman, Guzerat, and Tabapua animals using single‐ and multi‐breed analyses, with or without metafounders (MF) to model genetic differences across breeds. Records from the four breeding programs of the National Association of Breeders and Researchers (ANCP—Ribeirão Preto, SP, Brazil) were used. Data included pedigree (4.2 M), phenotypes (329 K), and genotypes (63.5 K) across all breeds. The number of genotyped animals within each breed was 58,574 for Nellore, 3102 for Brahman, 1389 for Guzerat, and 427 for Tabapua. The analysed traits were adjusted weight at 210 (W210) and 450 (W450) days of age and the scrotal circumference at 365 (SC365) days of age. IP were derived as the sum of the SNP effects weighted by the gene content using different reference populations: multi‐breed with or without MF, Nellore, or within‐breed. Scenarios were compared using the linear regression (LR) method for bias, dispersion, and accuracy. Adding MF decreased bias and under‐ or overdispersion and slightly increased the accuracy of IP. Combining breeds increased the accuracy of IP, mainly benefiting breeds with a small number of genotypes. These findings suggest that when young genotyped animals are not included in an official multi‐breed evaluation in zebuine cattle from Brazil, robust IP can be obtained with proper modelling, regardless of the breed. This helps obtain fast genomic predictions for young animals without overwhelming the evaluation system with too many animals.

Sperm morphology (form and size of sperm) analysis is useful for evaluating bull fertility and diagnosing reproductive performance. An advanced age is associated with a higher frequency of morphological sperm anomalies; however, there is limited information on the effect of aging and scrotal circumference on sperm morphological defects in Brahman cattle. The objective of this study was to investigate changes related to age and scrotal circumference on sperm morphology in Brahman bulls in Costa Rica. Brahman bulls are traditionally used in Costa Rican production systems. Sperm morphology was evaluated in 51 Brahman bulls from six age groups (< 24, 24–36, 37–48, 49–60, 61–72, and >72 months old) and scrotal circumference (32–36, 37–41, 42–46, and > 47 cm). The Trumorph® system was used for fixation. A total of 112 ejaculates and 200 sperm cells were analyzed per sample. Sperm defects were classified according to the 2021 World Health Organization laboratory manual and classification of University of Queensland Sperm Morphology Standardization Program. There was a higher frequency of anomalies in younger bulls (< 24 months old) and in those with a scrotal circumference >47 cm. A significant variation was found between the years analyzed, with significant differences (p < 0.05) of the year 2022 with respect to the others years. The most common defects by sperm region were loose heads and nuclear vacuoles, distal midpiece reflex, and bent tails. Deterioration related to age and scrotal circumference was observed in sperm morphology, with a higher defect frequency in bulls under 24 months of age and in those with a scrotal circumference >47 cm. Sperm morphology in Brahman bulls showed similar incidence regardless of sexual status (breeding or resting), but they varied according to age and scrotal circumference.