The liver is a central regulator of metabolic and endocrine functions that support fetal growth and postnatal development. Prenatal stress can reprogram hepatic development in the offspring, potentially causing long-term changes in metabolism and production efficiency. However, the influence of prenatal stress on hepatic molecular function and resulting phenotypes in beef cattle remains poorly understood. Therefore, the objectives of this study were to evaluate phenotypic traits and liver tissue gene expression in Brahman heifer and bull calves from prenatal transportation stress (PNS) and control (Control) treatment groups. One group of pregnant Brahman cows were transported for a 2-h period every 20 (±5) d from 60 to 140 days of gestation. Another group of pregnant Brahman cows served as Control. Thirty-two calves, eight heifer and eight bull calves from the PNS and Control groups, respectively, were utilized. Calves were weighed at approximately 25 (±2) d of age. The following day, calves were euthanized, and liver tissues were harvested. Phenotypic traits evaluated include birth weight, harvest weight, liver weight, pen score, and liver weight:harvest weight. Interaction of sex and treatment did not explain substantial variation for any trait (P > 0.28). Sex influenced birth weight, harvest weight, liver weight (P < 0.05), and treatment influenced liver weight:harvest weight (P < 0.10). Linear regression coefficients of traits on calf age as a linear covariate were not different from 0 (P > 0.41). Controlling false discovery rate at 0.10, there were no differentially expressed genes for PNS relative to Control and 13 differentially expressed genes for male relative to female comparisons. No genes were found to be differentially expressed across all comparisons. It is possible that the few differences between sexes and treatments may be due to relatively small sample sizes or to an unknown adaptation mechanism to the stress prenatally induced by this young age. Heightening the severity of prenatal transportation stress through increased duration or frequency of transportation may result in more differentially expressed genes.

Background/Objectives: The experience of prenatal stress results in various physiological disorders due to an alteration of an offspring’s methylome and transcriptome. The objective of this study was to determine whether PNS affects DNA methylation (DNAm) and gene expression in the stress axis tissues of mature Brahman cows. Methods: Samples were collected from the paraventricular nucleus (PVN), anterior pituitary (PIT), and adrenal cortex (AC) of 5-year-old Brahman cows that were prenatally exposed to either transportation stress (PNS, n = 6) or were not transported (Control, n = 8). The isolated DNA and RNA samples were, respectively, used for methylation and RNA-Seq analyses. A gene ontology and KEGG pathway enrichment analysis of each data set within each sample tissue was conducted with the DAVID Functional Annotation Tool. Results: The DNAm analysis revealed 3, 64, and 99 hypomethylated and 2, 93, and 90 hypermethylated CpG sites (FDR < 0.15) within the PVN, PIT, and AC, respectively. The RNA-Seq analysis revealed 6, 25, and 5 differentially expressed genes (FDR < 0.15) in the PVN, PIT, and AC, respectively, that were up-regulated in the PNS group relative to the Control group, as well as 24 genes in the PIT that were down-regulated. Based on the enrichment analysis, several developmental and cellular processes, such as maintenance of the actin cytoskeleton, cell motility, signal transduction, neurodevelopment, and synaptic function, were potentially modulated. Conclusions: The methylome and transcriptome were altered in the stress axis tissues of mature cows that had been exposed to prenatal transportation stress. These findings are relevant to understanding how prenatal experiences may affect postnatal neurological functions.

The interactive responses of cattle genetics and the rumen microbiome (G×M) govern variations in the feed efficiency and methane emissions, which subsequently impact cattle productivity and their environmental footprint. Modulation of the rumen microbiome can be done through dietary supplementation, such as with the antimicrobial ionophore monensin, which offers a pathway to favorably alter metabolic outcomes. However, the limited data on breed-specific microbiome shifts in response to dietary changes restrict the understanding of the impacts of G×M on fermentation and nutrient utilization. The objective of the study was to determine the effect of a monensin-fed diet on the ruminal microbiome and the short-chain fatty acid (SCFA) profile of temperate and tropically adapted cattle breeds. A total of 10 steers each of the Angus, Brahman, and F1 (Angus × Brahman) breed types were fed forage ± a monensin ionophore supplement. Ruminal fluid samples were collected during four 21-day periods (one equilibrium and three treatments). At the conclusion of each period, the SCFAs were analyzed via gas chromatography. The microbiome profiles were analyzed through DNA extraction, quantitative PCR (qPCR) assays, and sequencing to evaluate the G×M interactions. SCFA analysis showed a decrease in the acetate/propionate ratio ( p = 0.001) across all breed types under monensin treatment. However, breed type variations were evident, as the total SCFA concentrations were lower only in the Brahman steers that consumed monensin. The qPCR assays indicated significantly lower ruminal methanogen contents ( mcrA gene; p < 0.01) and a reduced methanogen/prokaryote ratio (MPR; p < 0.001) in monensin-fed steers compared with the control. A treatment-by-breed interaction was observed for the fungi/prokaryote ratio (FBR; p = 0.003), with only F1 steers on the monensin diet showing a lower FBR than those on the control diet. The permutational analysis of variance (PERMANOVA) and beta diversity analyses demonstrated significant differences in the ruminal microbiome structure between the control and the monensin-treated groups for both prokaryotic and fungal communities. Several amplicon sequence variants (ASVs) within the genera Faecalimonas , Streptococcus , and Prevotella showed variable abundance among breeds in response to monensin treatment, confirming the influence of (G×M) interactions on the microbiome structure. This study established the potential of dietary supplementation with an antimicrobial ionophore (monensin) to modulate the rumen microbiome structure, alter the metabolic profiles, and reduce methanogens while emphasizing the need for breed-specific dietary strategies due to the influence of G×M interactions.

As the amygdala is associated with fear and anxiety, it is important to determine the potential effects of gestational stressors on behavior and stress responses in offspring. The objective of this study was to investigate the effects of prenatal transportation stress on amygdala gene expression in 25-day-old Brahman calves, focusing on sex-specific differences. Amygdala tissue samples from prenatally stressed (PNS) and control bull and heifer calves were analyzed using RNA sequencing. A thorough outlier detection process, utilizing visual inspection of multidimensional scaling plots, robust principal component analysis, and PCAGrid methods, led to the exclusion of 5 of 32 samples from subsequent analyses. Differential expression analysis revealed no significant treatment differences between the control and PNS groups within either sex. However, sex-specific differences in gene expression were identified in both the control and PNS groups. The control group showed seven differentially expressed genes between sexes, while ten were identified between PNS males and females, with seven located on the X chromosome. Among these was the ubiquitin-specific peptidase 9 X-linked gene, which plays a role in neurodevelopmental pathways. When comparing males to females, regardless of treatment, a total of 58 genes were differentially expressed, with 45 showing increased expression in females. Gene enrichment analysis indicated that many differentially expressed genes are associated with infectious disease-related pathways. Future research should explore amygdala size and functional responses to various postnatal stimuli.

Abstract Prenatal stress (PNS) and early life adversity have been linked to epigenetic changes in the nervous, immune, and endocrine systems in various species. Previously, we reported that PNS calves had greater serum concentrations of ACTH and cortisol, were more temperamental, and had differential methylation of leukocyte DNA. The purpose of this study was to determine whether prenatal transportation stress differentially affected gene expression in the adrenal gland of calves. Mature Brahman cows inseminated to a single Brahman sire were assigned to either Control (n = 35; not transported) or PNS (n = 37; 2 h of transportation at 60, 80, 100, 120, and 140 ± 5 d of gestation) group. From some of these cows, 8 Control and 8 PNS bull calves were humanely euthanized at 25 ± 2 d of age. Adrenal glands were obtained, separated into the cortical (AC) and medullary (AM) components, placed into cryovials, snap frozen in liquid nitrogen, and stored at -80°C. Frozen samples (200 mg) were submitted to Novogene Corporation for RNA sequencing analysis on an Illumina Novaseq 6000 platform to generate 150 bp paired-end reads. The reference genome was Bos taurus ARS-UCD1.2. The DESeq2 R package was used for differential gene expression analysis (DEG) and DEGs (P ≤ 0.05, log2FC ≥ 1) were evaluated for gene ontology (GO) subclass terms and Kyoto encyclopedia of genes and genomes (KEGG) enrichment pathways. For the AC DEG comparison, a total of 899 genes were identified, with 641 upregulated and 258 downregulated in PNS calves. The AC DEGs were in the cellular component, molecular function and biological process GO subclasses related to circadian rhythm, lymphocyte proliferation, cytokine regulation, muscle development, and lipid metabolism. The KEGG enrichment analysis identified nitrogen metabolism, cytokine signaling, and circadian rhythm pathways associated with DEG of the AC. For the AM DEG comparison, a total of 1,245 genes were identified, with 745 upregulated and 500 downregulated in the PNS calves. The AM DEGs were in GO subclasses related to skeletal muscle development, antigen processing, and neural crest development. The KEGG enrichment analysis identified cell adhesion, viral infection, cytokine signaling, and amphetamine pathways associated with DEG of the AM. These early results suggest that prenatal stress differentially affects expression of genes of the adrenal cortex and adrenal medulla, which may affect health and growth of calves.Support: USDA NIFA Award No. 2019-67015-29573

Abstract Various managerial, nutritional, and environmental stressors may cause excessive production of reactive oxygen species (ROS) or free radicals which can damage cells and tissues, referred to as oxidative stress. Oxidative stress may impair beef cattle growth performance and product quality. Antioxidant enzymes are important in mitigating increased ROS to prevent oxidative stress, yet little is known about skeletal muscle antioxidant status in beef cattle of different breeds, ages and temperaments. We aimed to test the hypotheses that activities of antioxidant enzymes, glutathione peroxidase (GPx) and superoxide dismutase (SOD), in skeletal muscle would be greater in 1) Angus compared with Brahman steers; 2) longissimus thoracis (LT) compared with trapezius (TRAP) muscles; and 3) calm compared with temperamental animals. Brahman and Angus steers were classified as either calm (n = 13 Angus, n = 12 Brahman), intermediate (n = 11 Angus, n = 10 Brahman), or temperamental (n = 12 Angus, n = 12 Brahman) based on their pen score and exit velocity at weaning. Samples were collected from the LT and TRAP muscles of the steers at 10, 13, and 18 mo of age. Commercial assay kits were used to determine muscle GPx and SOD activities (Cayman Chemical, Ann Arbor, MI). Data were analyzed using linear models in SAS v9.4 with breed, age, temperament, breed × temperament, breed × muscle, and breed × age as fixed effects. Age was included as a repeated effect with animal within breed as the subject. Across muscle groups, Angus had greater GPx and SOD activities than Brahman (P < 0.0001). Additionally, GPx activity increased in both Angus and Brahman steers from 10 to 18 mo (P < 0.0001). In both breeds, the TRAP muscle had greater GPx activity than LT muscle (P < 0.0001). Brahman TRAP muscle also had greater SOD activity than Brahman LT muscle (P < 0.0001) but SOD activity was similar between muscle groups in Angus steers. Neither GPx nor SOD activity differed by temperament group in either breed or muscle group. These data suggest differences in skeletal muscle antioxidant status between Angus and Brahman steers which may mitigate oxidative stress, impacting growth performance as well as product quality at harvest.

Objective: Our objective was to expand the understanding of Bos indicus feed efficiency by utilizing Hereford x Brahman steers to determine if residual feed intake (RFI), residual average daily gain (RADG), and residual intake and gain (RIG) influence carcass and steak characteristics. Materials and Methods: Hereford x Brahman steers (n = 29; age + SD = 261 + 41 d) were transported to a facility with a GrowSafe System (GrowSafe Systems Ltd.) to determine RFI, RADG, and RIG, then to a feedyard (BW of 391 + 39.0 kg), fed 89 d, and slaughtered (BW 731 + 70 kg). Steers were categorized on their value compared with the mean (x) for RFI, RADG, and RIG into groups of efficient, less efficient, less inefficient, and inefficient. Results and Discussion: Efficiency measurements RFI, RADG, and RIG were not correlated with carcass or steak characteristics. Carcasses from less inefficient RADG steers had the least internal fat. Carcasses from less efficient RIG steers had the most adjusted backfat, and less inefficient RIG steers had lower yield grades than the less efficient and inefficient RIG steers. Steaks from the less inefficient RFI steers were tougher than the efficient and less efficient RFI. All other carcass and steak characteristics were not different. Implications and Applications: The results provide information about RFI, RADG, and RIG for Brahmaninfluenced herds and consideration of the small sample size should occur when applying the information to management decisions for beef herds.

The objective of this study was to determine if sire or dam had a stronger impact on age at first parturition of Brahman heifers (n = 833) born between 2000-2021. Typically, in Bos taurus heifers, puberty occurs between 10 to 12 mo of age leading to parturition of the first calf occurring around 24 mo of age. However, in Bos indicus cattle, puberty is achieved between 15 to 17 mo of age leading to a first calf around 36 mo of age. The ability of heifers to achieve pubertal status earlier plays a vital role in reproductive success. For selection purposes, knowing if early pubertal attainment is influenced more by the sire or dam is important for herd management. For this study, to minimize any epigenetic and environmental changes, all heifers originated and were developed at the Texas A&M AgriLife Research Center at Overton. Sire groups (SG) and dam groups (DG) were established based on the number of offspring used in the study. Sire groups were comprised of SG-1 (1+ calves sired; n = 58 sires), SG-2 (5+ calves sired; n = 44 sires), SG-3 (10+ calves sired; n = 31 sires), SG-4 (15+ calves sired; n = 23 sires), SG-5 (20+ calves sired; n = 17 sires), and SG-6 (25+ calves sired; n = 12 sires). Dam groups consisted of DG-1 (1+ calves; n = 489 dams), DG-2 (2+ calves; n = 215 dams), DG-3 (3+ calves; n = 81 dams), DG-4 (4+ calves; n = 38 dams), and DG-5 (5+ calves; n = 9 dams). Statistical analysis (PROC GLM; SAS 9.4) included the fixed effect of sire group (dam group) and all dams (sires) utilized in that grouping. Significance for age at first calving was considered at P < 0.05. Mean separation for age was performed using LSmeans. Sire significantly impacted age at first calving in SG-1 (P = 0.0173) vs dam effect (P = 0.3993; n = 489 dams), SG-2 (P = 0.0159) vs dam effect (P = 0.5476; n = 481 dams), SG-3 (P = 0.0023) vs dam effect (P = 0.2532; n = 439 dams), SG-4 (P = 0.0022) vs dam effect (P = 0.3997; n = 400 dams), SG-5 (P = 0.0002) vs dam effect (P = 0.0602; n = 361 dams), and SG-6 (P = 0.0005) vs dam effect (P = 0.1058; n = 305 dams). The dam impact on age at first calving was never significant in the dam groupings but sires did impact age at first calving in two groups: DG-1 (P = 0.3993) vs sire effect (P = 0.0173; n = 58 sires), DG-2 (P = 0.4823) vs sire effect (P = 0.0173; n = 56 sires), DG-3 (P = 0.3011) vs sire effect (P = 0.3420; n = 49 sires), DG-4 (P = 0.3911) vs sire effect (P = 0.6278; n = 40 sires), and DG-5 (P = 0.3042) vs sire effect (P = 0.9159; n = 23 sires). In summary, evaluation of sire and dam influences on age at first parturition for female offspring demonstrates that the ability to calve at an earlier age is influenced by the sire but not the dam. Further studies into the mechanisms for the transmission of this trait are warranted.

Background Temperament is an important production trait in cattle and multiple strategies had been developed to generate molecular markers to assist animal selection. As nonsynonymous single nucleotide polymorphisms are markers with the potential to affect gene functions, they could be useful to predict phenotypic effects. Genetic selection of less stress-responsive, temperamental animals is desirable from an economic and welfare point of view. Methods and results Two nonsynonymous single nucleotide polymorphisms identified in HTR1B and SLC18A2 candidate genes for temperament were analyzed in silico to determine their effects on protein structure. Those nsSNPs allowing changes in proteins were selected for a temperament association analysis in a Brahman population. Transversion effects on protein structure were evaluated in silico for each amino acid change model, revealing structural changes in the proteins of the HTR1B and SLC18A2 genes. The selected nsSNPs were genotyped in a Brahman population ( n = 138), and their genotypic effects on three temperament traits were analyzed: exit velocity, pen score, and temperament score. Only the SNP rs209984404-HTR1B (C/A) showed a significant association ( P = 0.0144) with pen score. The heterozygous genotype showed a pen score value 1.17 points lower than that of the homozygous CC genotype. Conclusion The results showed that in silico analysis could direct the selection of nsSNPs with the potential to change the protein. Non-synonymous single nucleotide polymorphisms causing structural changes and reduced protein stability were identified. Only rs209984404-HTR1B shows that the allele affecting protein stability was associated with the genotype linked to docility in cattle.

Comprehension of the genetic basis of temperament has been improved by recent advances in the identification of genes and genetic variants. However, due to the complexity of the temperament traits, the elucidation of the genetic architecture of temperament is incomplete. A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to analyze candidate genes related to bovine temperament, using bovine as the population, SNPs and genes as the exposure, and temperament test as the outcome, as principal search terms for population, exposure, and outcome (PEO) categories to define the scope of the search. The search results allowed the selection of 36 articles after removing duplicates and filtering by relevance. One hundred-two candidate genes associated with temperament traits were identified. The genes were further analyzed to construct an interaction network using the STRING database, resulting in 113 nodes and 346 interactions and the identification of 31 new candidate genes for temperament. Notably, the main genes identified were SST and members of the Kelch family. The candidate genes displayed interactions with pathways associated with different functions such as AMPA receptors, hormones, neuronal maintenance, protein signaling, neuronal regulation, serotonin synthesis, splicing, and ubiquitination activities. These new findings demonstrate the complexity of interconnected biological processes that regulate behavior and stress response in mammals. This insight now enables our targeted analysis of these newly identified temperament candidate genes in bovines.

Abstract Beef cattle breed and temperament are known to impact beef production; however, the physiological pathways linking stress and growth to palatability are not well understood. To test the hypothesis that live animal circulatory cortisol and insulin-like growth factor 1 (IGF1) would be related to temperament, production efficiency, and palatability, Brahman and Angus steers were classified as calm (n = 13 Angus; n = 12 Brahman), intermediate (n = 11 Angus; n = 10 Brahman), or temperamental (n = 12 Angus; n = 12 Brahman) based on their pen score and exit velocity at weaning. Serum samples collected at 10, 13, and 18 mo of age were evaluated for cortisol and IGF1 concentrations. Steers were maintained on grass pasture until they were moved to a feedlot after the 13-mo collection and provided a growing ration. Following the 18-mo collection, steers were sent to a commercial abattoir. Data were analyzed using linear models in SASv9.4 with breed, age, temperament, and all interactions as fixed effects and age as a repeated effect with animal(breed) as the subject. Relationships between variables were assessed with Pearson correlation coefficients. Calm Angus had greater IGF1 than temperamental Angus (P = 0.02) while intermediate Brahman had greater IGF1 than calm or temperamental Brahman (P ≤ 0.02). Temperamental Brahman had greater cortisol concentrations than calm and intermediate Brahman and temperamental Angus (P ≤ 0.01). In Angus, IGF1 concentrations decreased from 10 to 13 mo and from 13 to 18 mo (P ≤ 0.0006). In contrast, Brahman IGF1 concentrations increased with age to be greater at 13 and 18 mo than 10 mo (P ≤ 0.0001). Angus also had greater serum IGF1 than Brahman at 10 mo, but Brahman had greater IGF1 than Angus at 13 and 18 mo (P ≤ 0.0007). In 10 mo Brahman, IGF1 was positively correlated with animal body weight (BW) and average daily gain (P ≤ 0.005). IGF1 in 10 and 13 mo Brahman was also positively correlated with marbling (P ≤ 0.03). IGF1 in 13 mo Angus was positively correlated with Warner-Bratzler shear force (P = 0.02). Cortisol concentrations in Angus were greater at 10 and 13 mo than at 18 mo (P ≤ 0.004) leading to 10 mo Angus having greater cortisol concentrations than Brahman of the same age (P = 0.05). In Angus, at 10, 13, and 18 mo, cortisol was positively correlated with animal BW and hot carcass weight (P ≤ 0.05). At 10 and 13 mo, cortisol was positively correlated with ribeye area in Angus (P ≤ 0.005). These data suggest that serum IGF1 in Brahman is related to growth and lipid metabolism, and tenderness in Angus. However, cortisol concentrations have a more prevalent relationship with Angus growth and subsequently beef production. This project was supported by USDA NIFA Award #2021-67015-33392.

Abstract Supplementation (SUP) of stocker calves is used to enhance gain and/or adjust for stocking rates (SR). Our objective was to determine the influence of whole corn on performance of steers stocked on Tifton 85 bermudagrass [Cynodon dactylon (L.) Pers. X Cynodon nlemfuensis Vanderyst] (T85) that has documented forage crude protein ranging from 18.5% in June to 13.5% in September. For a 3-yr period, Brahman (Bos indicus) steers, 15 mo old and 275 kg body weight (BW), were stocked on T85 and received daily whole corn at 0 (PAS), 0.3% BW (SUP3), or 0.6% BW (SUP6). A fourth treatment included SUP6 at an increased stocking rate (SUP6SR). The 3-yr average SR of 275 kg steers was 11 steersּ ha-1 on PAS, SUP3, and SUP6, and 15 steersּ ha-1 on SUP6SR. Average daily gain (ADG) was similar for SUP steers at 0.98 kgּ d-1 (SUP6), 0.92 kgּ d-1 (SUP3), and 0.92 kgּ d-1 (SUP6SR), but greater (P = 0.002) than PAS steers at 0.84 kgּ d-1. Steer gainּ ha-1 was greatest (P = 0.001) for SUP6SR at 1230 kgּ ha-1. Gain ha-1 was similar for SUP6 and SUP3 at 1,010 kgּ ha-1 and 941 kgּ ha-1, respectively, and similar for SUP3 and PAS (860 kg-1). Body weights off pasture tended to be greater (P = 0.083) for all SUP steers at 370 kg than PAS steers at 354 kg. Body condition score off pasture was similar for all SUP steers at 5.7 and different (P = 0.001) from PAS steers at 5.2. At termination of stocking, steers were shipped 700 km to a commercial feedlot in South Texas. Each year, steers were fed in the same pen until a visual assessment of about 1.25 cm backfat was attained. Days on feed were similar for all steers at 190 d. Feedlot ADG was similar for steers on SUP3 (1.36 kgּ d-1), PAS (1.34 kgּ d-1), and SUP6SR (1.29 kgּ d-1), but greater (P = 0.045) than steers on SUP6 (1.24 kg d-1). These feedlot ADG exhibited some compensatory gain effects from pasture treatments. Off feedlot weights were similar at 620 kg. Steers were transported 60 km to an abattoir for harvest and carcass trait evaluations. There were no differences across treatments for steer hot carcass weight, 367 kg; 12th rib fat thickness, 1.13 cm; marbling score, 395; calculated yield grade, 3.10; longissimus dorsi area, 85.02 cm2; or internal fat (kidney-pelvic-heart), 1.92%. With SUP:extra gain at 12.5:1 for SUP3 and 13.8:1 for SUP6, supplementation of whole corn for Brahman steers stocked on T85 was not as efficient as previous T85 x SUP experiments with DDGS, but may offer management options for specific cattle classes and ownership-stocking strategies.

The objective of this study was to evaluate the effect of intronic single nucleotide polymorphisms (SNP) on temperament traits in a Brahman cattle population. The SNP located in CACNG4, EXOC4, NRXN3, and SLC9A4 candidate genes were genotyped in 250 animals with temperament records of exit velocity, pen score, and temperament score. Rs3423464051:G>A in the CACNG4 gene was associated with exit velocity and temperament score. An in silico analysis of the five intronic SNP showed that alternative alleles of CACNG4-rs3423464051, EXOC4-rs109393235, and SLC9A4-rs109722627 SNP could alter branch point sites during splicing, while a protein-protein interaction network analysis demonstrated a GRIA2 gene-mediated interaction between CACNG4 and NRXN3. The present results support previously reported evidence regarding bovine temperament-related candidate genes, particularly CACNG4, which is a confirmed candidate gene in need of more detailed analyses to reveal its role in temperament-related traits.

Mitochondrial abundance and efficiency correlate with meat color, but relationships between live animal mitochondria and other markers of beef quality remain largely unknown. To test the hypothesis that live animal skeletal muscle mitochondrial markers would be correlated with post-harvest hot carcass weight, ribeye area, calculated yield grade, backfat thickness, and marbling, samples were collected from the longissimus thoracis of Brahman and Angus steers at 10 mo (25 Angus, 23 Brahman), 13 mo (35 Angus, 33 Brahman), and 18 mo (35 Angus, 33 Brahman) of age. Mitochondrial volume density and function were quantified by citrate synthase (CS) and cytochrome c oxidase activities, respectively. Mitochondrial oxidative phosphorylation (OxP) and electron transfer (E) capacities were determined via high-resolution respirometry. Relationships between mitochondrial variables and carcass quality were determined using PROC CORR in SAS (v9.4). Within Angus at 10 mo, integrative (per mg tissue) complex I-supported OxP (PCI), maximal OxP (PCI+II), maximal E (ECI+II), and E supported by complex II (ECII) were positively correlated with hot carcass weight (P ≤ 0.05). Also, within 10 mo Angus, integrative OxPCI and flux control ratio (FCR) for OxPCI were positively correlated with backfat thickness (P ≤ 0.03). Within 10 mo Brahman, integrative PCI was positively correlated with ribeye area (P = 0.04). Within 13 mo Brahman, integrative mitochondrial proton LEAK was positively correlated with hot carcass weight (P = 0.02) and intrinsic (relative to CS activity) LEAK, PCI, and ECI+II were positively correlated with marbling (P ≤ 0.05). Conversely, CS activity was negatively correlated with marbling in 13 mo Brahman (P = 0.05). Integrative, FCR, and intrinsic LEAK were negatively correlated with ribeye area (P ≤ 0.05) but positively correlated with calculated yield grade in 13 mo Angus (P ≤ 0.03). However, at 18 mo, integrative, FCR, and intrinsic LEAK were positively correlated with ribeye area (P ≤ 0.008) but negatively correlated with calculated yield grade (P ≤ 0.01) in Angus steers. Furthermore, integrative and intrinsic OxPCI+II, ECI+II, and ECII were positively correlated with marbling in 18 mo Angus (P ≤ 0.04). Within 18 mo Brahman, CS activity was positively correlated with ribeye area (P = 0.006). Cytochrome c oxidase activity was not correlated with any markers of meat quality. These results suggest that mitochondrial capacity for energy production in Angus and Brahman steers at different life and production stages may dictate potential for skeletal muscle growth and lipid metabolism leading to differences in beef quality at slaughter. This project was supported by USDA NIFA Award #2021-67015-33392.

In cattle, prenatal transportation stress has been associated with differential methylation of genes related to metabolism, but the effects of prenatal transportation stress on skeletal muscle mitochondria and oxidative stress have not been investigated. We tested the hypothesis that prenatally stressed calves would exhibit increased skeletal muscle mitochondrial function resulting in greater oxidative stress than calves from non-stressed dams. Serum and longissimus thoracis muscle samples were collected from yearling Brahman calves whose mothers were stressed by transportation at five time points during gestation [i.e., prenatally stressed (PNS); eight bulls and six heifers] and control calves (CON; four bulls and six heifers). Serum was evaluated for concentration of the stress hormone, cortisol and for a marker of muscle perturbation, creatine kinase activity. Muscle samples were analyzed for concentration of a by-product of lipid peroxidation, malondialdehyde, and activity of the antioxidants, superoxide dismutase and glutathione peroxidase. Additionally, muscle mitochondrial volume density and function were estimated by citrate synthase and cytochrome c oxidase activities, respectively. Data were analyzed using mixed linear models with sex, treatment, and the sex × treatment interaction as fixed effects. No investigated variable differed between CON and PNS calves (p ≥ 0.3). These data suggest that prenatal transportation stress does not have an impact on skeletal muscle mitochondrial metabolism or markers of stress or muscle damage in Brahman yearling calves at rest. However, previously reported negative impacts of prenatal stress on inflammatory responses suggest that PNS calves may be differentially equipped to handle an acute stressor. Future research should investigate the energetic and inflammatory implications of acute stressors in animals subjected to prenatal stress.

Selecting high-immune-responding cattle benefits the individual animal and the herd. To assess factors that have a role in determining the immune status of cattle, this study used 55 weaned bull and 57 weaned heifer Brahman calves. Antibody-mediated immune response (AMIR) was determined by using a vaccine-specific IgG, enzyme-linked immunosorbent assay (ELISA) in response to cattle receiving the Salmonella Newport Extract vaccine. Cell-mediated immune response (CMIR) was determined by using a subcutaneous (neck) sensitization dose of Candida albicans (CA) with Quil-A adjuvant on Day 0. On Day 14, caudal skinfold thickness (SFT) was measured using Harpenden calipers prior to the intradermal injection of CA into the skinfold, and on Day 15, the injection site SFT was measured again. The response was determined by using the difference in SFT from Day 15 (post-injection) and Day 14 (pre-injection). In weaned Brahman calves, AMIR was not influenced by sex; however, there was sexual dimorphism associated with CMIR, in that bull calves had a greater response than heifers (p < 0.05). Our studies demonstrate that weaned Brahman calves can be separated into AMIR and CMIR classes and that AMIR and CMIR should be investigated further as selection tools in beef cattle production.

The 3′ untranslated region has an important role in gene regulation through microRNAs, and it has been estimated that microRNAs regulate up to 50% of coding genes in mammals. With the aim of allelic variant identification of 3′ untranslated region microRNA seed sites, the 3′ untranslated region was searched for seed sites of four temperament-associated genes (CACNG4, EXOC4, NRXN3, and SLC9A4). The microRNA seed sites were predicted in the four genes, and the CACNG4 gene had the greatest number with 12 predictions. To search for variants affecting the predicted microRNA seed sites, the four 3′ untranslated regions were re-sequenced in a Brahman cattle population. Eleven single nucleotide polymorphisms were identified in the CACNG4, and eleven in the SLC9A4. Rs522648682:T>G of the CACNG4 gene was located at the predicted seed site for bta-miR-191. Rs522648682:T>G evidenced an association with both exit velocity (p = 0.0054) and temperament score (p = 0.0097). The genotype TT had a lower mean exit velocity (2.93 ± 0.4 m/s) compared with the TG and GG genotypes (3.91 ± 0.46 m/s and 3.67 ± 0.46 m/s, respectively). The allele associated with the temperamental phenotype antagonizes the seed site, disrupting the bta-miR-191 recognition. The G allele of CACNG4-rs522648682 has the potential to influence bovine temperament through a mechanism associated with unspecific recognition of bta-miR-191.