Cattle Research Articles

Temperament of the dairy cow relates to her maternal behaviour in a pasture-based extended suckling system

Cow-calf rearing is gaining interest in dairy systems as an alternative to calf separation soon after birth. One commonly articulated benefit of these ‘extended suckling’ systems is that they allow expression of highly motivated maternal behaviours. The quality of maternal expression is subject to natural variation, however, and could be influenced by the temperamental characteristics of the dam. This study assessed the relationship between cow temperamental characteristics and expression of maternal behaviours in a pasture-based extended suckling system. Sixteen dairy cows (Bos taurus) underwent social isolation, novel object and novel human tests at 4 months of pregnancy. A principal components analysis (PCA) was used to determine associations between cow responses in these tests. After parturition, the cows entered an extended suckling system (half-day contact) until calves were weaned. Cow-calf interactions at pasture were video recorded for 4 consecutive hours (∼09:00 AM – 1:00 PM) at weeks 3, 6 and 9 post-partum. These data were used to calculate a maternal behaviour score for cows by subtracting the frequency of “negative” maternal behaviours (i.e., agonistic behaviour delivered to own calf, rejecting own calf suckling attempt and rejecting attempted contact by own calf) from the frequency of “positive” maternal behaviours (i.e., nursing own calf, affiliative behaviour delivered to own calf and proximity to own calf). A Pearson correlation was then used to assess the relationship between factors scores and maternal scores. Three behavioural traits were identified from the PCA: boldness, anxiety and sociability. In general, cows delivered more affiliative behaviour to their calves than to other calves and to cows and nursed their own calf more than other calves. The maternal behaviour score varied (mean ± SD, 33 ± 13.4, minimum = 9, maximum = 49). Cows with higher loadings for boldness had a lower maternal behaviour score (p < 0.05). There was no correlation between maternal behaviour score and anxiety or sociability (p > 0.05). The lower maternal behaviour score of bold cows in this study might be influenced by their prioritisation of foraging and exploration over interactions with their calves. Despite the long-standing practice of calf separation soon after birth, the current study demonstrates that maternal abilities of pasture-based dairy dams persist. We conclude that cow temperamental characteristics are related to how the cows interacted with their calves.

Theoretical model of impact mitigation mechanisms inherent to the North American bison skull

ABSTRACT North American bison (Bovidae: Bison bison) incur blunt impacts to the interparietal and frontal bones when they engage in head-to-head fights. To investigate the impact mitigation of these bones, a finite element analysis (FEA) of the skull under loading conditions was performed. Based on anatomical and histological studies, the interparietal and frontal bones are both comprised of a combination of haversian and plexiform bone and are both underlain by bony septa. Additionally, the interparietal bone is thicker than the frontal bone. Data regarding the mechanical properties of bison bone are scarce, but the results of a phylogenetic analysis infer that the material properties of the closely related domestic cow bone are a suitable proxy for use in the FEA. Results of the FEA suggest that the thickness of the interparietal bone in conjunction with the bony septa may prevent fracture stresses by helping to absorb and disperse the blunt impact energy throughout the skull. Monotonic stress levels of 294 MPa, which are below the compressive strength of bone were exhibited in the simulated bison head impacts indicating no fracture of the bones.

PSIX-19 Effect of protein and starch level on N balance and ruminal fermentation parameters in steers consuming low-quality forage: Bos taurus taurus

Abstract Globally cattle convert low-quality forage to beef and milk; therefore, understanding protein utilization in Bos taurus taurus is critical to enhancing sustainability as over and under-supplementation of protein are economically and environmentally costly. Low-quality forage lacks the N necessary for proper utilization and metabolic function. Supplemental protein improves low-quality forage utilization and is expected to increase N absorption and retention. Supplement starch can increase volatile fatty acid (VFA) production and energy supplied to the animal; however, too much starch decreases ruminally available N and pH potentially decreasing fibrolytic activity. Accordingly, our objective was to determine the effect starch supplementation on N balance and ruminal fermentation parameters in Bos taurus steers. Ruminally cannulated Angus steers [n = 5; body weight (BW) = 375 ± 45 kg] were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. Supplemental N intake decreased linearly (P &amp;lt; 0.01) with increasing starch as the crude protein content of the soybean was underestimated. Forage and total N intake were not affected by starch level (P ≥ 0.17). Fecal and total urinary N excretion were not different between starch levels (P ≥ 0.43). Urinary ammonia-N and urea-N averaged 6.6 and 16.8% of total urinary N excretion, respectively, but no differences between starch levels were observed (P ≥ 0.39). Level of starch supplementation had no effect on N retention and absorption (P ≥ 0.50). There was a treatment × time interaction observed for ruminal ammonia concentration (P &amp;lt; 0.01). All treatments, except 2% starch, peaked at 4 h post feeding, 20 and 38% treatments gradually decreased following four, but the concentration of ruminal ammonia decreased by 80% between 4 h and 8 h after feeding in the 56% starch treatment. Starch level had no effect total VFA concentration, VFA molar proportions, or ruminal pH (P ≥ 0.10). In conclusion, providing supplemental starch did not affect N balance or VFA production when fed to steers consuming low-quality forage. Nitrogen balance and VFA production likely were not affected because all supplements provided sufficient ruminally available N and, therefore, exerted minimal effects on forage utilization.

PSX-15 Effect of starch supplementation on rumen bacterial abundance in Bos taurus indicus steers consuming low-quality forage

Abstract Deficient ruminally available nitrogen caused by a basal diet of low-quality forage can limit microbial growth in the rumen and decrease forage utilization. Protein supplementation is well-documented to improve forage digestibility and performance. Additionally, starch has been evaluated to increase energy supply to grazing cattle when the forage cannot support adequate levels of production. However, most research in this area has been conducted in Bos taurus taurus, especially the response of the rumen microbiome to supplementation. Accordingly, the objective of this study was to evaluate the effects of increasing starch supplementation on rumen bacterial populations in Bos taurus indicus steers supplemented protein and consuming low-quality forage. Ruminal samples were collected from five ruminally-cannulated Brahman steers (BW 420 ± 55 kg) used in a 4×4 Latin square fed a basal diet of King Ranch Bluestem Hay (3.5% CP and 73% NDF) provided ad libitum, and one of four isonitrogenous (130 mg N/kg BW) supplements with increasing levels of starch (2% starch= 100% soybean meal; 20% starch= 73% soybean meal, 26.2% corn, 0.8% urea; 38% starch = 47% soybean meal, 51.6% corn, 1.4% urea; 56% starch= 19% soybean meal, 78.6% corn, 2.4% urea). Rumen content samples were collected via rumen cannula at 4h post-feeding. Microbial DNA was extracted; full length 16S rRNA amplicon libraries were prepared using Kinnex kits and then sequenced on the PacBio Revio platform. Reads were analyzed using DADA2 and QIIME2. Statistical analysis was performed with the GLIMMIX procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC). Firmicutes, Bacteroidata, Actinobacteriota, Verrucomicrobiota, and Euryarchaeota were the most abundant phyla in all treatments (83, 10, 3, 0.4, and 1%, respectively), and were not affected by treatment (P ≥ 0.10). Christensenellaceae R-7 group, Rikenellaceae RC9 gut group, Lachnospiraceae-XPB1014-group, Butyrvibrio, Lachnospiraceae-NK3A20-group, and Prevotella represented the most abundant genera for all treatments (7, 5, 11, 9, 7, and 3%, respectively). Lachnospiraceae-XPB1014-group and Lachnospiraceae-NK3A20-group responded quadratically (P ≤ 0.02) to increasing starch with decreased abundance for the 20% and 38% starch supplement. Comparatively, relative abundance of Butyrvibrio responded quadratically (P &amp;lt; 0.01) with increased abundance in the 20% and 38% starch supplement. Pseudobutyrvibrio increased with supplementation of 20% starch and then decreased as starch supplementation increased (quadratic, P = 0.04). In conclusion, supplementation of starch elicited changes in microbial relative abundance at the genus level with the response in Butyrivibrio suggesting greater fibrolytic activity. Forage and total digestible NDF intake in these steers decreased with increased starch supplementation; however, TDOMI was not affected by starch provision.

Evolution and mutational landscape of highly pathogenic avian influenza strain A(H5N1) in the current outbreak in the USA and global landscape

The emergence of highly pathogenic avian influenza strain A (H5N1) in the USA is a high concern. Here, we illustrated the evolution, divergence, transmission pattern, infection pattern, entropy diversity, nucleotide diversity, and mutational landscape of HPAI(H5N1). We depicted three phylogenetic trees, i.e., from three perspectives: considering the HPAI H5N1 genome of the current outbreak in the USA (n = 971), considering the HPAI H5N1 spared in different hosts (cattle, hunan, avian, and nonhuman primates) and using the global genome sequences (n = 3154). We found that the clade 2.3.4.4b was responsible for the present infection. We noted that the USA's divergence rate is 3.43e-3 subs per site per year, and the global divergence rate is 5.21e-3 subs per site per year. We reported significant nucleotide changes to illustrate the genome.Similarly, we observe several point mutations in some proteins, such as PB2, PA, HA, NA, and NS1. Among point mutations, some common mutations are noted in PB2 (E362G, M631L) and PA (L219I, K497R). However, elimination strategies should be a high priority for dairy farm workers, domestic cattle, and poultry birds to limit future outbreaks.

PSVI-24 Gene expression profiles of granulosa and peripheral white blood cells from fertile and sub-fertile beef heifers

Abstract Beef heifer fertility issues contribute to a major economic loss in the cow-calf production industry. Therefore, identifying beef heifers with superior genetic potential for improved fertility would increase profitability. This study aimed to identify differences in the transcriptome profiles from granulosa and peripheral white blood cells (pWBCs) of beef heifers with varying reproductive potential. For this, Angus-Simmental crossbred heifers were subjected to an estrus synchronization and fixed-time artificial insemination (AI) protocol (7-D CO-Synch + CIDR) followed by exposure for 60-d to a fertile bull. Depending on the presence or absence of conceptus 120 d post-AI, heifers were classified as fertile (pregnant by AI) or sub-fertile (non-pregnant by AI or bull-breeding). Pregnancies were terminated, and all animals in both groups (fertile, n = 8; and sub-fertile, n = 5) were cycling when the blood and ovaries were collected from each heifer. Total RNA was extracted from the pWBCs and granulosa cells and subjected to library preparation and sequencing on the Nova-Seq platform. The read counts were obtained after data quality control using FastQC v0.11.9 and MultiQC v1.12 and alignment to the Ensemble’s ARS UCD1.2 Bos taurus genome reference using STAR aligner v2.7.5. The filtered data were subjected to differential expression analysis using DESeq2. We identified 1,061 and 72 significantly differentially expressed genes (DEGs) with P-values ≤ 0.05 and absolute (log2 fold change) ≥ 0.5 from pWBC and granulosa, respectively. Notably, 12 targets including 9 protein coding genes (PLCL1, DNER, GNAS, CDH3, PER1, ITGA2B, CXCL12, ENSBTAG00000048613, ENSBTAG00000051519), bta-mir-2887-1, 5-8S-rRNA and U5 were found as DEGs in both the tissues. Based on a differential co-expression analysis using PCIT, we identified GNAS and DNER as hub genes in pWBC and the granulosa cells of the sub-fertile heifer group. The 12 shared genes were over-represented for pathways such as NF kappa B and chemokine signaling, regulation of actin cytoskeleton, and platelet activation. Some of the identified genes have been previously associated with fertility, while others are novel. A detailed understanding of the underlying biological mechanisms of the top genes and a follow-up study with a larger sample size at different time points could validate the candidates identified in this study for their role as potential therapeutic targets.

PSV-15 Evaluating the relationship between subcutaneous backfat thickness and sperm morphology in young beef bulls

Abstract Literature indicates that high-energy diets can lead to reductions in both sperm motility and morphology in bulls. This study aimed to investigate the relationship between individual variation in subcutaneous backfat thickness (SCBF) and sperm morphology in young beef bulls exposed to the same diet. We hypothesized that bulls with excessive subcutaneous fat thickness have increased sperm morphology defects compared with bulls with adequate subcutaneous backfat thickness. Historical data collected from yearling Bos taurus beef bulls (n = 557) enrolled in a bull development program were used in an observational retrospective cohort study to test this hypothesis. Over the course of 5 yr, bulls in two locations were developed according to industry standard practices, and performance was evaluated over 84 d with a 21-d adaptation period. At the end of the performance evaluation period, a carcass ultrasound was performed to evaluate ribeye area, SCBF, and intramuscular fat. Furthermore, breeding soundness examinations (BSE) were performed according to the Society of Theriogenology guidelines within 40 d after carcass ultrasonography. Bulls that failed the BSE for reasons unrelated to semen quality were excluded from this study. Within each year, bulls were ranked based on SCBF and classified as top 10% (TOP; n = 55), middle 80% (MID; n = 446), and bottom 10% (BTM;n = 56) for SCBF. Initial body weight (BW) was greater (P &amp;lt; 0.01) in TOP bulls compared with MID and BTM (Table 1). Off-test BW was also greater in TOP compared with MID and BTM bulls (P &amp;lt; 0.01). In contrast, average daily gain and scrotal circumference did not differ between experimental groups (P = 0.35 and P = 0.65, respectively). TOP bulls had greater (P &amp;lt; 0.01) SCBF compared with MID and BTM, and MID bulls had greater (P &amp;lt; 0.01) SCBF compared with BTM bulls. Similar results were observed for intramuscular fat (P &amp;lt; 0.01) and ribeye area (P &amp;lt; 0.01). Percentage of normal sperm cells was greater in both BTM and MID bulls compared with TOP bulls (P &amp;lt; 0.01). Additionally, percentage of primary abnormalities tended (P = 0.07) to be greater in TOP bulls compared with BTM and MID. There were no differences in the percentage of secondary abnormalities between experimental groups (P = 0.45). There was a tendency (P = 0.07) for a greater percentage of TOP bulls to fail the BSE compared with MID and BTM bulls. Moreover, there was a positive linear relationship (P = 0.01) between SCBF and the probability of failing the BSE. In summary, elevated SCBF in bulls exposed to the same diet was associated with an increase in sperm morphological abnormalities and tended to increase the percentage of bulls failing the BSE.

PSIII-2 Exploring differential gene expression and pathways associated with pregnancy outcomes in beef heifers

Abstract Heifer fertility is a key factor in the success of beef production systems, as the reproductive performance of a heifer correlates with her stayability in the breeding herd. However, despite being reproductively mature and physically healthy, 5 to 15% of these heifers fail to conceive within a designated breeding season. The underlying physiological mechanisms preventing these heifers from achieving pregnancy remain elusive. Therefore, this study aimed to determine differentially expressed genes (DEGs) and biological pathways associated with pregnancy outcomes in beef heifers. Angus-Simmental crossbred heifers were subjected to an estrus synchronization and fixed-time artificial insemination (AI) program (7-d CO-Synch + CIDR) and blood samples were collected at the time of AI for isolation of peripheral white blood cells (PWBC). After pregnancy check, heifers were classified as pregnant (P) and non-pregnant (NP). Based on that, 6 animals per group were randomly selected for total RNA isolation from the PWBC samples, and genome-wide expression was measured through RNA sequencing. The RNA-Seq data were analyzed using an in-house bioinformatics pipeline, with filtered reads aligned to the Bos taurus reference genome using STAR. DEGs were identified using DESeq2, followed by functional analysis using ShinyGO. Our approach unveiled 230 DEGs, comprising 102 up and 128 downregulated genes in the NP group (P-value ≤ 0.05 and |log2FC| &amp;gt; 0.5). Upregulated genes included those from the cytochrome P450 superfamily (CYP27B1 and CYP2U1). The genes SCML2, USIG2, and FBP1 were upregulated and have been associated with immune response and increased PWBC counts. This may be related to the over-representation of biological processes involved in cell division based on the upregulated genes. KEGG pathway over-representation analysis of DEGs retrieved allograft rejection, graft-versus-host disease, type I Diabetes Mellitus, insulin signaling pathway, and transcriptional misregulation of cancer. These pathways included genes such as BOLA-DQB, PRKAR1B, CALML4 and JUP, which were reported as downregulated during times of inflammatory response. Another downregulated gene was GZMB, which is needed for proper cell targeting during immune response. This finding may provide a link between immune function and early pregnancy failure. However, the relationship between the immune system and pregnancy warrants further investigation. Our results shed light on the molecular mechanisms underlying reproductive performance in beef heifers and support previous studies associating immune function with pregnancy outcomes. These differentially expressed genes may be further explored as potential avenues for enhancing fertility in beef production systems.

PSXIII-18 Prenatal transportation differentially affects the adrenal cortical and adrenomedullary transcriptomes of Brahman bull calves

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

50 Awardee Talk: The role of non-traditional inheritance patterns among Bos indicus-Bos taurus crosses for global beef value chain considerations

Abstract Bos indicus-Bos taurus crosses have been effectively used in many production environments globally. Substantially higher amounts of hybrid vigor have been reported in these F1 crosses as compared with those involving only Bos taurus or only Bos indicus breeds. However, for many years, and in many environments, “unusual” aspects of calf growth have been documented among these crosses. Among F1 crosses, Bos indicus-sired calves (Bos indicus x Bos taurus) have birth weight 8 to 12 kg heavier than contemporary Bos taurus-sired calves (Bos taurus x Bos indicus); additionally, pronounced sexual dimorphism occurs where males may weigh 5 to 10 kg more than females from Bos indicus sires (Bos taurus dams) but 1 kg or less from Bos taurus sires (Bos indicus dams) in both natural service and embryo transfer calves. These reciprocal differences have been reported for fetal and placentome size mid gestation. Reciprocal differences in birth weight have also been reported among backcrosses and F2 calves, and also exist for longer gestation length from Bos indicus sires (Bos taurus dams). Increased birth weight and gestation length occur when more Bos indicus is present in the sire vs. the dam, and when Bos indicus influence is inherited through the sire vs. the dam. There is speculation that sex-specific genomic imprinting may be involved for reciprocal birth weight differences that are analogous to mouse interspecific crosses for litter weight. Reports of hybrid vigor retention among inter se matings after the F1 have been variable historically, and this variation may relate to how the foundational F1 parents were produced (Bos indicus- vs. Bos taurus-sired). Breed-of-origin haplotype on BTA5 has been shown to affect heifer pregnancy and rebreeding among F2 Nellore-Angus cows where Nellore-derived haplotypes had much lower performance compared with Angus-derived and hybrid haplotypes. Disproportionate calf sex has been reported among reciprocal F2 Nellore (Bos indicus)-Angus (Bos taurus) with 66.6% male calves from Nellore x Angus F1 sires. When retrospectively evaluating historical literature for reciprocal crosses, it appears that several instances occur with disproportionate calf sex percentage, and this phenomenon warrants further study. The extent that potential reciprocal differences may affect post-weaning growth and carcass traits has not been widely evaluated. Recent investigations have shown reciprocal F1 differences for some cell-mediated immune responses regarding T-lymphocyte proliferation, but no differences for humoral response. There needs to be additional research that completely characterizes the X chromosome of Bos indicus and Bos taurus origins and their roles for multiple production traits. There also needs to be more investigation of non-additive and parent-of-origin effects in genetic evaluations of Bos indicus-Bos taurus composites, particularly with desired first-generation breed percentage. Improved utilization of Bos indicus cattle and crosses will be instrumental in meeting global dietary protein demands.

77 Differences in carcass quality and meat quality between cattle of different breed types

Abstract Crossbreeding cattle in the beef industry is a common practice to improve production and increase profitability. Introducing Bos indicus (BI) genetics into cattle herds is one potential method to improve production, as they are able to withstand higher temperatures, are better adapted to nutritional stress, and consume less water than Bos taurus (BT) cattle. However, introduction of BI genetics is known to decrease both carcass and meat quality compared with those from BT cattle. As such, the objective of this study was to determine how crossbreeding commercial Angus cows with Santa Gertrudis bulls to incorporate BI genetics impacts carcass and meat quality of the resultant offspring. This study utilized 38 steers of two different breeds: Angus (AN; n = 29; 100% BT) or Santa Gertrudis influenced (SG; n = 9; 19% BI, 81% BT). All steers were fed the same typical ration and harvested at a commercial facility once industry average body weight and backfat standards were met. Hot carcass weight (HCW), ribeye area (REA), yield grade (YG), and marbling scores were collected at harvest. Individual loins were collected for meat quality analysis. Meat quality data were collected after 14 d of wet aging at 4˚C. Meat color data was collected on d 0, 3, and 7. Statistical analysis was done using the MIXED procedure of SAS to assess the main effect of breed. Color analysis was conducted with day as a repeated measure. Least squares means were separated using Tukey-Kramer adjustments. Angus cattle had an increased (P = 0.009) REA and tended to have a reduced (P = 0.06) YG than SG cattle. However, no differences (P ≥ 0.13) between breeds were observed in HCW or marbling score. Additionally, no differences (P ≥ 0.08) were observed in meat quality (pH, drip loss, cook loss, Warner-Bratzler Shear Force, or Texture Profile Analysis) between breeds. There was not a day x breed (P &amp;gt; 0.65) or breed (P ≥ 0.57) effect for L*, a*, or b* color values. Day affected (P = 0.008) L*, a*, and b*, such that a* and b* both increased on d 3, then decreased on d 7, while L* increased on d 3 and remained consistent until d 7. These results are promising as they indicate there may not be differences in carcass quality and meat quality when utilizing this method to introduce BI genetics into a traditional BT production system. As such, this could be a useful tool in managing production systems in our beef herds. However, future research with a larger sample size will be necessary to gain more conclusive results.

144 Assessing economic implications of thermal stress of Bos indicus and Bos taurus species during finishing in northern Colorado

Abstract The objective of this study was to determine the economic implications of thermal stress on climate adaptive capacity, resiliency, and impact of Bos indicus and Bos taurus finishing steers using common finishing systems. The experimental design was a completely randomized design, with a 2 by 2 factorial arrangement of finishing system (‘natural’ or ‘conventional’) and species of cattle (Bos indicus or Bos taurus). Steers [n = 200; body weight (BW) ~450 kg] were housed in 20 feedlot pens (10 steers/pen) for the first 84 d, where cattle were blocked by initial BW. For the remainder of the 180 d (96 d) finishing period, cattle were moved to four Climate Smart Research Pens (50 steers/pen, 1 pen/ treatment, and species combination). Within each Climate Smart Research Pen, five SmartFeed systems were used to evaluate individual animal feed intake, one GreenFeed emission measurement system was used to evaluate individual animal gas emissions flux of enteric CH4, O2, H2, and CO2, and were equipped for nutrient mass balance of carbon, nitrogen, and phosphorus. Animal BW were collected every 28 d for analysis of average daily gain (ADG) and feed efficiency. Thermal stress behaviors were evaluated by one trained personnel on a subset of 7 steers/treatment via the measurement of respiration rate, open mouth breathing, rumen temperature, number of daily water intake events, lying and standing behavior, and pen surface temperature for the last 96 d of the finishing period. At harvest, carcass characteristics, liver scores, and heart scores were collected. Economic analyses were conducted post-hoc to determine the profitability of each species based on economic implications, tradeoffs, carcass quality and quantity, and time to finish. Selection of cattle for climate adaptive features may involve production tradeoffs (e.g., depressed rate of gain, greater yield risk, lower technical efficiency) and adjustment costs (e.g., re-optimizing feed for a new breed), which affect the adoption of less common breeds into the US cattle supply chain. Adding to the complexity of this evaluation, consumers preferences may not adapt quickly, affecting the prospect of Bos indicus cuts of meat in the market. We also, therefore, explore the supply- and demand-side effects of climate change adaptation through breed selection in the beef industry.

479 Pain control for the castration of newborn bull calves by elastration

Abstract All methods of castration are known to cause pain regardless of the method, or age of the animal. Our objective was to explore providing pain control for bull calves castrated by elastration prior to 1 wk of age. Singleton, bull calves (n = 85) born at the Ontario Beef Research Centre were enrolled and randomly assigned to 1 of 5 treatment groups at birth: a single dose of oral meloxicam at castration (1ORAL), a dose of oral meloxicam at castration and a second oral dose 1 wk later (2ORAL), a dose of injectable meloxicam at castration (1INJECT), not castrated (SHAM), or castrated without pain control (PAINFUL). Calves were treated within 48 h of birth and followed until weaning. All calves were observed 2 h/d for 13 different pain-associated behaviors (e.g., tail flicks, kicking, licking the scrotum) on the day of castration (d 0), as well as d 1, 2, 7, 8, and 9. To record general activity, from d -1 to d 14 each calf wore an Onset HOBO Pendant G Data Logger attached to one of their hind legs. Calves were weighed weekly until they were turned-out to pasture and thereafter weighed bi-weekly until weaning. Five behaviors were statistically significant between treatment groups. PAINFUL calves had roughly three times the rate of licking (P &amp;gt; 0.05) compared with calves in 1ORAL, 2ORAL, and 1INJECT groups, and four times the rate of licking compared with SHAM calves. Additionally, PAINFUL calves had two times the rate of tail flicks (P &amp;lt; 0.05) compared with meloxicam-treated calves, and five times the rate of tail flicks compared with SHAM calves. A treatment effect (P &amp;lt; 0.05) was observed for standing time, with PAINFUL calves spending the least amount of time standing on average in a 24-h period. No statistical time differences were seen between the remaining treatment groups. No treatment or treatment*time interaction effects were observed for lying time. A tendency was seen for treatment effect on lying time (P = 0.0581), with PAINFUL calves spending the most time lying on average and having a significance difference compared with all other treatment groups (LSM &amp;gt; 0.05). No treatment effect was seen for average daily gain up to wk 8, and for final weaning weights. Weight at time of castration was significant (P &amp;lt; 0.05); however, calves were not blocked by BW when assigned to treatment. In conclusion, meloxicam-treated calves expressed decreased rates of pain-associated behaviors compared with PAINFUL calves, and BW did not differ at time of weaning. Our results provide evidence that calves castrated by elastration before 1 wk of age and received meloxicam, experience less pain.

386 Pregnancy supportive metabolites are enhanced in Brahman cows on day 15 of the estrous cycle

Abstract Bos indicus-influenced cattle are more resilient to pregnancy loss while receiving a restricted nutrient diet compared with Bos taurus cattle, but the mechanism behind this resilience is still unknown. To undercover this mechanism, the present study was designed with Angus (Bos taurus), Brangus (Bos indicus-influenced), and Brahman (Bos indicus) cows randomly assigned (d -30) to either a 100% maintenance diet (n = 22), or a 70% maintenance diet (n = 23) for 45 d. All cows were submitted to a 5-d CO-Synch + CIDR synchronization protocol on d -7 with ovulation induction representing d 0. A cervically navigated foley catheter was placed in the uterine horn ipsilateral to the corpus luteum on d 15 of the estrous cycle. Approximately 50 mL of phosphate buffered saline was infused into the uterus then recovered for uterine flush analysis. Recovered uterine fluid was subjected to metabolomic analysis by ultra-high performance liquid chromatography - high resolution mass spectrometry. A significant breed by metabolite interaction occurred (P &amp;lt; 0.001). A treatment by metabolite interaction was also observed (P = 0.015) in which maintenance and restricted cows clustered within their respective treatment when plotted in an orthogonal PCA graph. Of the 101 metabolites analyzed, 7 metabolites (aspartate, glutamate, hydroxyphenylacetate, taurine, uric acid, uridine, and xanthine) differed (P &amp;lt; 0.05) among breeds. Brahman cows had the greatest value of all 7 metabolites (P &amp;lt; 0.05) except hydroxyphenylacetate (P &amp;gt; 0.10). Angus and Brangus metabolomic values were similar for aspartate, taurine, and uridine (P &amp;gt; 0.10) but differed for glutamate, hydroxyphenylacetate, uric acid, and xanthine (P &amp;lt; 0.05). Two metabolites that were greatest in Brahman cows (aspartate and glutamate) contribute significantly to the Kreb Cycle, indicating that Brahman cows have the ability to maintain proper amounts of substrates for energy production compared with Angus cows. Both glutamate and aspartate also aid in the removal of toxic ammonium as they are substrates for a-ketoglutarate and oxaloacetate, respectively, which both consume ammonium in their respective reactions. Furthermore, uric acid (which has a precursor of xanthine) was also greatest in Brahman cows and is a potent antioxidant with strong capabilities of scattering reactive oxygen species. Finally, aspartate also aids in the detoxification of ammonium within the urea cycle. Taken together, these four metabolites (aspartate, glutamate, uric acid, and xanthine) are working together but separately with the overall goal to provide more functional energy, while removing unnecessary toxins which may be two mechanisms in how Bos indicus-influenced cows are better able to sustain optimal reproductive efficiency than Angus cows.

401 Effect of protein and starch supplementation level on intake and digestibility by steers consuming low-quality forage: I. Bos taurus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage depresses forage utilization. Supplemental protein improves forage utilization by increasing RAN, resulting in increased intake and potentially improving digestion. Addition of starch to a supplement can increase total digestible organic matter (OM) intake (TDOMI); however, too much starch decreases RAN and pH potentially decreasing forage utilization. Our objective was to determine the effect of starch supplementation on intake and digestion in Bos taurus indicus steers. Accordingly, five ruminally cannulated Brahman steers [body weight (BW) = 420 ± 55 kg) were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/ kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. As designed, supplement OM intake (SOMI) increased linearly (P &amp;lt; 0.01) as starch level increased. Other measures of intake, including forage OM intake (FOMI), total OM intake (TOMI), and total neutral detergent fiber intake (TNDFI) decreased in a cubic manner in response to increasing starch (P ≤ 0.04). Forage OMI also responded with a cubic decrease (72.2, 68.9, and 69.5 g/kg BW0.75) when the protein supplement contained 2, 20, and 38% starch, respectively, but decreased to 61.2 g/kg BW0.75 when the 56% starch supplement was provided. Similarly, TOMI decreased 5.3% when starch inclusion increased from 38 to 56%. Total tract OM digestion and NDF digestion were not significantly affected (P ≥ 0.86) by starch level in the supplement; therefore, despite TOMI and TNDFI decreasing, there was no effect on total digestible OM intake and (TDOMI) and total digestible NDF intake (TDNDFI). In conclusion, providing supplemental starch over 38% decreased forage utilization. Decreases in FOMI with starch inclusion may be attributed to competition for RAN between fiber fermenting and starch fermenting bacteria.

Altered microRNA composition in the uterine lumen fluid in cattle (Bos taurus) pregnancies initiated by artificial insemination or transfer of an in vitro produced embryo

BackgroundMicroRNAs (miRNAs) are presented in the uterine lumen of many mammals, and in vitro experiments have determined that several miRNAs are important for the regulation of endometrial and trophoblast functions. Our aim was to identify and contrast the miRNAs present in extracellular vesicles (EVs) in the uterine lumen fluid (ULF) at the onset of attachment in cattle pregnancies (gestation d 18) initiated by artificial insemination (AI) or by the transfer of an in vitro-produced blastocyst (IVP-ET). A third group had no conceptus after the transfer of an IVP embryo.ResultsThe abundance of 263 annotated miRNAs was quantified in the EVs collected from ULF. There was an increase in the transcript abundance of 20 miRNAs in the ULF EVs from the AI pregnant group, while 4 miRNAs had a lower abundance relative to the group not containing a conceptus. Additionally, 4 miRNAs were more abundant in ULF EVs in the AI pregnant group relative to IVP-ET group (bta-mir-17, bta-mir-7-3, MIR7-1, MIR18A). Specific miRNAs in the ULF EVs were co-expressed with messenger RNAs expressed in extra-embryonic tissues and endometrium, including genes that are known to be their targets.ConclusionsThe results provide biological insights into the participation of miRNAs in the regulation of trophoblast proliferation and differentiation, as well as in endometrium receptivity. The knowledge that in vitro cultured embryos can contribute to the altered abundance of specific miRNAs in the uterine lumen can lead to the development of corrective approaches to reduce conceptus losses during the first month of pregnancy in cattle.

247 Interaction between colostrum and milk replacer supply on growth, development and fecal consistency of dairy surplus calves

Abstract This study examined the interactions between early life nutrition strategies and their impact on growth, development, and fecal consistency in surplus bull calves. Holstein-Friesian bull calves [n = 120; body weight (BW) = 43.1±3.56 kg] were enrolled. In the first 12 h after birth, calves were fed either 2 L (100 g of IgG) or 6L (300 g of IgG) of colostrum replacer (CR) to obtain either failure (F) or successful (S) transfer of passive immunity, respectively. Upon arrival at the facility, serum IgG concentrations were measured; therefore, F and S calves were identified accordingly and randomly assigned to one of two milk replacer (MR) feeding schemes: Moderate (Mod; ~8 L) or Low (Low; ~4 L). In total, there were 4 treatments resulting from the 2 × 2 factorial design: F-Mod, F-Low, S-Mod, S-Low (n = 30/treatment). Calves were individually housed and fed twice daily until d 42, gradually weaned until d 56, and had free access to straw and water during the study. On d 22, a calf pelleted starter was offered. To evaluate organ and gastroinstetinal tract development, 10 calves/treatment were euthanized at 84 d of age. Other measurements include weekly BW, daily intakes, and daily fecal score until d 21. Data were analyzed by PROC MIXED in SAS accounting for the fixed effects of block, CR, MR, and time, and their interaction. Time entered the model as a repeated statement, and initial BW was used as a covariable when appropriate. Initial BW was not different across treatments, whereas serum IgG was greater in S calves (S = 1,962.9 vs. F = 941.0 mg IgG/dL). During the study, BW was influenced by both CR (P = 0.001) and MR (P &amp;lt; 0.001), where S and Mod calves consistently exhibited greater BW when compared with F and Low calves, respectively. At d 84, Mod calves (F-Mod and S-Mod) were on average 18 kg heavier than Low calves. Similarly, Mod calves exhibited greater fresh tissue weights in the liver, pancreas, spleen, and both the small and large intestines (P &amp;lt; 0.05). Starter intake was influenced by MR (P &amp;lt; 0.001), with Low calves having the greatest intake before and during weaning. However, post-weaning starter intake was greater (P = 0.010) in Mod calves. Fecal consistency was influenced by CR (P = 0.001) and MR (P &amp;lt; 0.001), with S and Low calves having improved fecal consistency. Although no interactions were observed between CR and MR, these findings underscore the importance of considering both colostrum and MR levels in calf nutrition management to optimize growth and improve animal welfare during the early stages of life.

143 Short- and long-term effects of heat stress in cow-calf pairs adapted to tropical and subtropical regions

Abstract Chronic exposure to high temperatures and humidity can limit beef cattle performance in tropical/subtropical environments, regardless of breed. Despite better heat adaptability compared with Bos taurus cattle, heat-stressed Bos indicus cattle also experience an increase in body temperature above the physiological limit. As body temperature increases, cascades of behavioral and physiological events are triggered to lessen heat load but often at the expense of productive outcomes. Contrary to other species and feedlot beef cattle, the effects of heat stress on physiology and performance of grazing cow-calf pairs have not been evaluated in detail, particularly for Bos indicus cattle. Preliminary data showed opposite outcomes to heat stress in Bos indicus vs. Bos taurus cattle, limiting the implications of the existing data generated from studies using beef and dairy Bos taurus cattle. This presentation will share some nutritional and management practices to mitigate heat stress in grazing beef cattle. Practices mentioned herein include altering the timing of body weight (BW) growth pattern (stair-step, SST) and immunomodulatory feed ingredient (IFI) supplementation for replacement beef heifers, and maternal access to shade to reduce heat load. For 100 d before the breeding season, Bos indicus-influenced beef heifers grazing warm-season grasses received a constant supplementation amount or SST strategy (50 d of low then 50 d of high supplementation), with or without IFI. Under severe heat stress conditions, IFI supplementation reduced heifer vaginal temperature but did not increase their growth and reproduction, whereas the SST strategy lowered internal body temperature, enhanced growth performance and pregnancy success compared with a conventional constant supplementation practice. Our group is also focused on the critical need to determine the specific effects of heat stress mitigation during pre- and postnatal phases on physiology and performance of Bos indicus-influenced cow-calf pairs. Study 1 evaluated the impacts of maternal access to artificial shade from 83 d prepartum until 50 d postpartum on body thermoregulation, performance, and physiology of beef heifers and their first offspring. Removing maternal access to shade led to greater maternal respiration rate, vaginal and body surface temperatures and reduced maternal body condition score and calf BW at birth. Nonetheless, offspring born from cows with no access to shade were remarkably heavier during a 60-d post-weaning period and had decreased plasma indicators of inflammation and positive effects to humoral immune response. Study 2 is a multi-year, USDA/NIFA-funded study designed to capitalize on the ability of cattle to reprogram physiological/immunological systems following exposure to stress during gestation. Study 2 combined gestational and postnatal heat abatement to enhance the overall growth/immune/reproductive performance of grazing Bos indicus-influenced cow-calf pairs. Partial data on long-term growth and reproductive performance, physiology, metabolome, and microbiome of both cows and their female offspring will be shared in this presentation.

189 Association of the liver phosphoproteome with divergent dry matter intake in finishing beef steers

Abstract As the need for improving the sustainability of the beef industry increases, optimizing feed efficiency is of the utmost importance. The liver has a central role in nutrient metabolism, and for ruminants particularly, it is essential for providing glucose through gluconeogenesis via substrates such as propionate, lactate, and glycerol. Further, through cell signaling and vagal afferent signals, the liver acts to stimulate and inhibit dry matter intake (DMI). Thus, the objective of this study was to investigate alterations in the phosphoproteome of finishing beef steers in relation to divergent DMI to identify changes in the abundance of signaling proteins. Angus steers [n = 57; initial body weight (BW) = 518 ± 27 kg] underwent a 63-d intake trial utilizing an Insentec Roughage Intake Control System (Hokofarm Group, Emmeloord, The Netherlands). Prior to beginning the trial, liver biopsy samples were collected from all steers. Samples from steers with the greatest and least DMI (n = 8 each) were utilized for phosphoproteomic analysis. Liver protein was isolated and labeled with isobaric tandem mass tagging reagents. Samples were enriched for phosphopeptides using immobilized metal affinity chromatography and subsequently analyzed using high-performance liquid chromatography tandem mass spectrometry. Spectral data were searched in the National Center for Biotechnology Information Bos taurus protein database using MaxQuant (version 2.2.0.0; Max Planck Inst., Munich, Germany), and the data were analyzed using Perseus (version 2.0.10.0; Max Planck Inst.). Two sample t-tests were conducted to determine the difference in phosphopeptide abundance between steers with high and low DMI. A total of 16,365 phosphopeptides were identified, and 287 were differentially expressed (False Discovery Rate &amp;lt; 0.05). In addition, 2,777 phosphopeptides were differentially expressed based on an unadjusted P &amp;lt; 0.05 which were used for enrichment analysis of Gene Ontology processes and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways using the Database for Annotation, Visualization, and Integrated Discovery. The background for this analysis was all identified phosphopeptides. Gene ontology terms enriched included processes related to phosphorylation activity, intracellular signal transduction, response to insulin, kinase activity, and signaling protein binding. Enriched KEGG pathways included pathways related to insulin signaling, such as AMPK signaling, mTOR signaling, and MAPK signaling. Further, pathways related to glycolysis and gluconeogenesis, glucagon signaling, insulin resistance, carbon metabolism, and various other signaling pathways were also enriched. These results suggest a link between the liver phosphoproteome and DMI, indicating that divergent DMI is associated with alterations in signaling pathways related to nutrient uptake and metabolic processes.

228 Evaluation of sire vs. dam influences on age at first parturition in Brahman heifers

Abstract 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&amp;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 &amp;lt; 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.