Beef Herds Research Articles

Fitness benefits of grouping during foraging in beef cattle: Social behaviour or affinity to vegetation resources?

Grouping behaviour in gregarious species expresses a dynamic cost-benefit equilibrium. The balance between costs and benefits differs amongst individuals that were selected to maximize their individual fitness. In environments where resources are limited, benefits of grouping may come at the expense of increased competition over resources. This study aimed to test whether grouping behaviour during foraging in a free-ranging beef cattle herd is a social choice bearing fitness benefits for all participants, or reflects affinity to vegetation resources with possible differentiating fitness benefits. GPS location data were recorded in a herd of 60 beef cows grazing a semi-arid pasture in northern Israel. Pasture vegetation was chemically and spectrally analysed. GPS location data were used to investigate individual and shared foraging locations and the temporal sequence of initiating foraging movement. Co-travel function in ArcPro v3.0 was used to investigate the amount and variability of individual proximity associations and their correlation with fitness. Fitness proxies were conception result (yes/no) and the interval between calving and conception within the cows who conceived. A positive correlation was found between fitness and the individual number of proximity associations, but not with the variability in associations' partners. No significant correlations were found between fitness and vegetation biomass, N content and spectral properties measured by REEVI2 index in foraging locations. Individual sequence of arrival at shared foraging locations and foraging movement initiation sequence were also not correlated with fitness. Vegetation biomass in grouping locations was lower than in individually foraged locations, but no difference was found in N content between individual and shared foraging locations. No differences were found in vegetation biomass and N content between herd foraging locations and random locations, thus no evidence for herd foraging strategy aimed to increase biomass or N consumption was found. No further differences in pasture resources availability, i.e., water, shade, human or predator presence could explain grouping. Circular variance values implied the absence of preferred movement direction. Our results suggest that grouping during foraging is fitness beneficial and is not related to vegetation biomass or N content. Our results further suggest the absence of consistent leading individuals and no significant correlations between foraging movement initiation and fitness. This study provides insights into social and vegetation factors affecting cattle foraging behaviour in constrained pasture, and may allow ranchers to improve grazing management systems. We suggest that further research into pasture characteristics that affect beef cattle pasture location choice is needed.

Analysis of factors associated with the first lumpy skin disease outbreaks in naïve cattle herds in different regions of Thailand.

Thailand experienced a nationwide outbreak of lumpy skin disease (LSD) in 2021, highlighting the need for effective prevention and control strategies. This study aimed to identify herd-level risk factors associated with LSD outbreaks in beef cattle herds across different regions of Thailand. A case-control study was conducted in upper northeastern, northeastern, and central regions, where face-to-face interviews were conducted with farmers using a semi-structured questionnaire. Univariable and multivariable mixed effect logistic regression analyses were employed to determine the factors associated with LSD outbreaks. A total of 489 beef herds, including 161 LSD outbreak herds and 328 non-LSD herds, were investigated. Results showed that 66% of farmers have operated beef herds for more than five years. There were very few animal movements during the outbreak period. None of the cattle had been vaccinated with LSD vaccines. Insects that have the potential to act as vectors for LSD were observed in all herds. Thirty-four percent of farmers have implemented insect control measures. The final mixed effect logistic regression model identified herds operating for more than five years (odds ratio [OR]: 1.62, 95% confidence interval [CI]: 1.04-2.53) and the absence of insect control management on the herd (OR: 2.05, 95% CI: 1.29-3.25) to be associated with LSD outbreaks. The implementation of insect-vector control measures in areas at risk of LSD, especially for herds without vaccination against the disease, should be emphasized. This study provides the first report on risk factors for LSD outbreaks in naïve cattle herds in Thailand and offers useful information for the development of LSD prevention and control programs within the country's context.

Bovine viral diarrhoea viruses from New Zealand belong predominantly to the BVDV-1a genotype

Aim To determine which genotypes of bovine viral diarrhoea virus (BVDV) circulate among cattle in New Zealand. Methods Samples comprised BVDV-1-positive sera sourced from submissions to veterinary diagnostic laboratories in 2019 (n = 25), 2020 (n = 59) and 2022 (n = 74) from both beef and dairy herds, as well as archival BVDV-1 isolates (n = 5). Fragments of the 5′ untranslated region (5′ UTR) and glycoprotein E2 coding sequence of the BVDV genome were amplified and sequenced. The sequences were aligned to each other and to international BVDV-1 sequences to determine their similarities and phylogenetic relationships. The 5′ UTR sequences were also used to create genetic haplotype networks to determine if they were correlated with selected traits (location, type of farm, and year of collection). Results The 5′ UTR sequences from New Zealand BVDV were closely related to each other, with pairwise identities between 89% and 100%. All clustered together and were designated as BVDV-1a (n = 144) or BVDV-1c (n = 5). There was no evidence of a correlation between the 5′ UTR sequence and the geographical origin within the country, year of collection or the type of farm. Partial E2 sequences from New Zealand BVDV (n = 76) showed 74–100% identity to each other and clustered in two main groups. The subtype assignment based on the E2 sequence was the same as based on the 5′ UTR analysis. This is the first comprehensive analysis of genomic variability of contemporary New Zealand BVDV based on the analysis of the non-coding (5′ UTR) and coding (E2) sequences. Conclusions and clinical relevance Knowledge of the diversity of the viruses circulating in the country is a prerequisite for the development of effective control strategies, including a selection of suitable vaccines. The data presented suggest that New Zealand BVDV are relatively homogeneous, which should facilitate eradication efforts including selection or development of the most suitable vaccines.

Evolution over the last 40 years of the assisted reproduction technologies in cattle - the Brazilian perspective I - timed artificial insemination.

The reproductive efficiency of the herd is correlated with higher productivity in livestock. Reproduction biotechniques, such as ovulation synchronization protocols, are important to optimize production and accelerate genetic profit in beef and dairy herds. The objective of this review is to describe the evolution over the last 40 years of the artificial insemination (AI) and the timed-AI (TAI) protocols in cattle from a Brazilian perspective. TAI protocols are based on synchronizing emergence of the wave of follicular growth, controlling circulating progesterone (P4) concentrations, stimulating the final growth of the follicle and inducing a synchronized ovulation. Hormonal alternatives that optimize the response at the end of the protocol and strategies to induce final follicle growth and ovulation in categories of females with low expression of estrus are described. Furthermore, the potential positive effect of previous exposure to injectable P4 on fertility of Bos indicus and Bos taurus cows is also discussed.

Factors Influencing Productivity and Sustainability of Small-Scale Beef Farms in Thailand

Over the past few decades, Thailand has witnessed a decline in production from small-scale beef cattle farming, accompanied by a reduced interest from younger generations in continuing family farming. The present study aimed to determine the state of these farms based on good agricultural practices (GAP) and explored factors influencing beef herd productivity and the willingness of the next generation to sustain the family business. Data from 1,175 questionnaires from 34 provinces was analyzed using SPSS. Beef herds with higher calving rates (CR ≥ 60%) had better herd, reproductive, and health management scores compared with the lower CR (<60%) group. Results from a negative binomial regression showed that factors, i.e., prediction of calving date and routine deworming positively impacted CR, while others like feeding types, mineral supplements, vaccination and hormonal estrus synchronization negatively correlated with CR. Expert opinions (N = 83) highlighted the importance of recording systems, heat detection programs, pregnancy diagnosis, feeding type, sufficient qualified water supply and mineral supplements. The use of Artificial Neural Network (ANN) and GLM analysis also noted that farm potential score, farmer gender, and occupations were pivotal for the sustainability of beef farming. This research aids in strategizing for enhanced sustainable beef production in Thailand.

Rumen and fecal microbiomes are related to diet and production traits in Bos indicus beef cattle.

Ruminants harbor a complex microbial community within their gastrointestinal tract, which plays major roles in their health and physiology. Brazil is one of the largest producers of beef in the world and more than 90% of the beef cattle herds are composed of pure and crossbred Nelore (Bos indicus). Despite its importance to the Brazilian economy and human feeding, few studies have characterized the Nelore microbiome. Therefore, using shotgun metagenomics, we investigated the impact of diet on the composition and functionality of the Nelore microbiome, and explored the associations between specific microbial taxa and their functionality with feed efficiency and methane emission. The ruminal microbiome exhibited significantly higher microbial diversity, distinctive taxonomic profile and variations in microbial functionality compared to the fecal microbiome, highlighting the distinct contributions of the microbiomes of these environments. Animals subjected to different dietary treatments exhibited significant differences in their microbiomes' archaeal diversity and in the abundance of 89 genera, as well as in the functions associated with the metabolism of components of each diet. Moreover, depending on the diet, feed-efficient animals and low methane emitters displayed higher microbial diversity in their fecal microbiome. Multiple genera were associated with an increase or decrease of the phenotypes. Upon analyzing the functions attributed to these taxa, we observed significant differences on the ruminal taxa associated with feed efficient and inefficient cattle. The ruminal taxa that characterized feed efficient cattle stood out for having significantly more functions related to carbohydrate metabolism, such as monosaccharides, di-/oligosaccharides and amino acids. The taxa associated with methane emission had functions associated with methanogenesis and the production of substrates that may influence methane production, such as hydrogen and formate. Our findings highlight the significant role of diet in shaping Nelore microbiomes and how its composition and functionality may affect production traits such as feed efficiency and methane emission. These insights provide valuable support for the implementation of novel feeding and biotechnological strategies.

Differences in the choice of beef artificial insemination sires used by dairy producers versus beef producers

The growing demand among dairy producers for suitable beef sires to mate to their females creates the possibility of separate breeding programs to generate beef sires for the dairy sector versus those for the beef sector. Informing such a decision is the extent of the genetic differences among beef sires used by dairy producers relative to those used by beef producers. The objective therefore of the present study was to use a large national database of artificial insemination (AI) records in dairy and beef cow herds to establish the difference in mean genetic merit of beef AI sires used by dairy producers versus those used by cow-calf beef producers. The traits explored were gestation length, calving difficulty, and perinatal mortality as well as the 3 carcass traits of carcass weight, conformation, and fat score. Carcass conformation and fat score are mechanically assessed on a scale of 1 (poor conformation and low fat cover) to 15 (excellent conformation and high fat cover). Sire genetic merit differences for feed intake and docility were also examined. Estimates of genetic merit for all 8 traits on individual AI sires available at the time of service were used. A total of 1,230,622 AI records comprised 909,719 services from dairy herds and 320,903 services from beef herds were used. Of the 1,802 beef AI sires represented in the entire dataset, over half were used by both dairy and beef herds representing ≥98% of the services in each production system. However, the usage rate of individual AI sires differed between dairy and beef herds with the Spearman rank correlation between the quantity of inseminations per sire in dairy and beef herds being just 0.38. This correlation means that beef AI sires used heavily in the beef herd were not always those heavily used in dairy herds. A clear difference in the mean genetic merit of beef AI sires selected by dairy producers relative to those selected by beef cow-calf producers was obvious with the extent of the difference being a function of whether the female served was a nulliparous heifer or a cow. Much of the differences in genetic merit of chosen beef AI sires between dairy and beef producers was actually attributable to differences in breed choice, albeit some within-breed selection was also evident. Irrespective, dairy producers, on average, chose shorter gestation length sires whose progeny were genetically less predisposed to require intervention during the birthing process; these sires had genetic merit estimates expected to result in lighter and less conformed progeny carcasses relative to the beef AI sires used by beef producers. Results point to large differences in genetic merit of the beef AI sires chosen by dairy versus beef producers, much of which actually reflected differences in breed choice among dairy and beef producers.

PSXIV-20 Genetic Differences Related to Beef Production Traits in Bos Taurus Or Bos Indicus Influenced Cattle

Abstract Global climate change has had, and will continue to have, a negative impact on cattle production. With the global population expected to exceed 9 billion people by 2050, improving production efficiency is imperative to optimizing use of available land and natural resources. One potential method of doing so is to increase the percentage of Bos indicus (BI) genetics in the US beef herd. Compared with Bos taurus (BT) cattle, BI influenced cattle are better adapted to nutritional stress, consume less water, are more heat resistant, and have increased resistance to parasites. The objective of this study was to examine the phenotypic and genotypic outcomes of introducing BI genetics into a BT herd in a temperate climate setting. This study included a live animal trial that utilized a total of 115 steers of two different breeds: Angus (AN; n = 83; 100% BT) or Santa Gertrudis influenced (SG; n = 32; 19% BI, 81% BT). All steers were fed a typical feedlot ration for the area in pens equipped with Vytelle units, weighed every 28 d throughout the trial, and harvested at a commercial facility once industry backfat standards were achieved. Breed did not have an effect (P >0.10) on dry matter intake, average daily gain, gain to feed, ribeye fat thickness, hot carcass weight, or USDA yield grade. Intramuscular fat was increased (P = 0.002) in AN steers, and there was a tendency (P = 0.09) for SG steers to spend more time with their heads down during bunk visits. To better examine the genomic differences between the two beef breeds, DNA from 88 (AN = 58, SG = 30) of the 115 steers was isolated. A Bovine GGP 100k assay was completed commercially, and data were analyzed using Excel and the Multi-Locus Mixed Model of SVS. The traits that were analyzed include average daily gain, gain to feed, dry matter intake, hot carcass weight, marbling score, cold camera ribeye size, ribeye fat thickness, and cold camera yield grade. For each trait, further evaluation was done on SNP markers with the greatest P-values. Differences in allelic combinations that contributed to statistical significance was observed in data attained from dry matter intake, hot carcass weight, marbling score, and cold camera yield grade. Further analysis suggested a potential breed effect on marbling score, cold camera yield grade, and cold camera ribeye size. Additional research is warranted to better understand the relationship between genetics and the observed phenotypic traits, as well as conducting similar analysis on feeding behavior characteristics.

PSIV-9 Describing the Consumption of Chlortetracycline-Containing Supplement Offered Free-Choice to Commercial Beef Cows on Pasture

Abstract Extensive beef cattle production systems depend on forage as the predominant nutrient source. However, mineral requirements are not always met solely through forage consumption. To maintain optimum animal productivity, beef cattle producers must provide mineral supplementation and free-choice supplements are most common. Free-choice supplement intake by grazing cattle is highly variable and is dictated by season, individual animal preference, supplement palatability and other factors. Variation in supplement intake is problematic for delivering medication such as chlortetracycline (CTC), which is aimed to mitigate the risk of bovine anaplasmosis in beef herds. Research investigating the relationship between individual animal attributes and supplement consumption in extensive settings is limited. Recently, adoption of technology such as a portable, self-contained individual feeding unit (SmartFeed; C-Lock Inc.) into supplementation programs has facilitated unprecedented data collection in grazing cattle. The study objectives were to describe the consumption patterns of a granular CTC-containing supplement and to evaluate the factors contributing to consumption variability by gestating cows on pasture. A total of 103 nonlactating, pregnant, crossbred cows were assigned to this experiment on d -28 and allocated to 1 of 3 pastures equipped with a SmartFeed unit to record individual supplement intake. Cows were offered dried distillers grains for 27 d of acclimation to the units (mean intake of 0.29 kg of supplement/cow daily; 74% of cows) before transition to a commercially available granular mineral supplement containing CTC for 46 d. Supplement was formulated such that a 630 kg cow must consume 113 g/d to receive the label CTC dose (1.1 mg/kg). Cow intake and unit visit frequency data were analyzed using a general linear model (PROC GLM) and differences evaluated using Least Squared Means. The runs test for serial randomness was used to evaluate clustering of feeding and non-feeding events. Feeding and non-feeding events during the 46-d observation period were not randomly distributed (P < 0.01), and the mean number of consecutive days a cow did or did not consume mineral supplement were 1.8 and 5.6 days, respectively. As cow age increased, visits to the feeding unit decreased and total supplement consumption also decreased (P < 0.01). According to supplement label instructions, each cow was expected to consume 5.2 kg of supplement in total over 46 d to receive the total recommended 32.2 g CTC dose. Mean supplement consumption was 40.5 g· cow-1· d-1, providing 0.25 g CTC· cow-1· d-1, and only 1.9% (2/103 cows) consumed enough supplement to receive the recommended dose. Collectively, results indicate that providing a granular free-choice supplement containing CTC is not an effective method of ensuring cows consume an adequate amount of supplement to receive CTC at the label-directed dose and frequency.

131 How Horn Flies Could Be Affecting Your Beef herd's Reproductive Success

Abstract Horn flies (HF) are one of the most prevalent external parasites on pastured cattle in North America, although they can be found worldwide. HF cause animals severe stress leading to increased cardiac and respiratory rates, and decreased feed efficiency, average daily gain, and milk production. All these detrimental effects caused by HF contribute to over $1 dollars in economic loss in the United States, annually. Current methods of reducing fly numbers, including manure management, feed additives, and insecticides, are being utilized with varying degrees of success. However, these methods require extensive management, are temporary, and are costly to producers. While several studies have investigated the effects of horn flies on growth and milk production traits, there have been very few studies on their potential impacts on reproduction in beef cattle. Insemination and calving data collected on cows and yearling heifers at Northwest Georgia Research and Education Center between 2015 to 2022 was used to determine the effect of HF abundance on fertility. Each animal was exposed to two insemination events. Artificial Insemination (AI) was used except for cows that did not get pregnant from the first AI which were placed on pasture with a proven bull for natural service. The outcomes (success/failure) of each insemination event and calving were recorded. Still births where the dam carried the calf to term, but the calf passed during parturition were recorded as successes. As part of a research project, no fly control methods were carried out on the farms during 2019 and 2022. During these years, images of each animal were taken twice between May and August. The best image of each animal was used to estimate HF count. Animals were placed in three abundance classes (Low: 0-150, Med: 151-400, High: 401+) to analyze the effects of fly abundance on reproduction. For the remaining years (2015-2018, 2020-2021) animals received fly control and were not assessed for fly abundance. As shown Table 1, conception rates of each breeding attempt and calving rates were lower in both years where no horn fly control was used (2019 and 2022) compared with the remaining years where fly control was utilized. The decrease in conception rates when no fly control was used suggests a detrimental effect of HF on reproductive success. Additionally, for the animals measured in 2022, the average fly count for the dams who did not calf successfully was 357 which is significantly higher than the average count for the dams who did successfully calf (290). This suggests that animals with greater fly loads are less likely to carry to term. These adverse effects on reproductive health could be mitigated by genetically selecting for animals that can tolerate a greater fly load.

168 Characterization of the Culturable Fraction of Bovine Ocular Microbiota and Its in Vitro Antimicrobial Activities Against Pinkeye Pathogens

Abstract Pinkeye, clinically known as infectious bovine keratoconjunctivitis (IBK), is considered one of the most important ocular diseases in cattle, causing an estimated $226 million in annual losses to U.S. cow-calf producers. While Moraxella bovis is considered the principal IBK pathogen, Moraxella bovoculi has also been associated with the pathogenesis of IBK. Thus, these Moraxella species are often the target for antibiotic and/or vaccine-based treatment and prevention strategies. Despite extensive use of antibiotics, IBK infections are challenging to treat, highlighting the increased need for an antibiotic-alternative approach to control IBK. Recent evidence suggests that the microbial community associated with the bovine oculus is important for eye health, and that the ocular microbiota can be a target for enhancing disease resistance against IBK in cattle. The objectives of this study were to characterize the ocular microbiota of healthy and IBK infected cattle using sequencing and culturing techniques, and to isolate and screen commensal ocular isolates for their antimicrobial activity against M. bovis and M. bovoculi. Ocular swabs (n = 64) were collected using eSwabs from cattle diagnosed with IBK or without IBK (healthy control) before antibiotic treatment from beef herds across North Dakota. Swabs were plated onto four different agar plates (blood, Columbia blood, MRS and multi-sliced agar plates), and cultured aerobically and anaerobically. A total of 658 bacterial isolates were obtained via culturing and cryopreserved. Taxonomic identification was performed on a subset of banked isolates (n = 277) by near full-length sequencing of the 16S rRNA gene. These isolates taxonomically belong to 6 different bacterial phyla: Bacillus (42%), Firmicutes (27%), Actinomycetota (13%), Pseudomonadota (11%), Actinobacteria (5%), and Proteobacteria (2%). A total of 55 different genera were identified with Bacillus (25%), Streptococcus (13%), Staphylococcus (10%), Moraxella (6%), Macrococcus (5%), Paenibacillus (3%), Caldibacillus (3%), and Rummeliibacillus (3%) being the most dominant genera. Next, a subset of these commensal isolates (n 53) were screened for their growth inhibition against M. bovis and M. bovoculi using an agar slab method. Among the screened isolates, 6 isolates showed inhibition against M. bovis and M. bovoculi with zones of inhibition ranging from 12 mm to 28 mm. Ocular isolates identified as Weizmannia coagulans (43Y-MRSC), Lentillactobacillus buchneri (23D-MRSA) and Paenibacillus polymyxa (785-WCF) exhibited relatively strong inhibition against both Moraxella isolates. Scanning electron microscopy revealed noticeable structural and morphological damages in M. bovis and M. bovoculi cells due to Weizmannia coagulans culture-supernatant treatment. Overall, our results indicate that ocular mucosa of beef cattle is inhabited by relatively rich and diverse culturable bacterial communities, and that some ocular commensals can inhibit IBK pathogens. This suggests the potential for the development of bacterial therapeutics based on commensal ocular bacteria to mitigate IBK in cattle.

PSIII-30 Effects of a Bacillus-Based Direct-Fed Microbial on in Vitro Gas Production and Fiber Digestibility of Feedstuffs

Abstract Direct-fed microbials (DFM) support the health and performance of the herd through different modes of action, including improvements on nutrient digestibility. In fact, Bacillus spp. has been identified as an important enzyme-producing bacteria that could benefit overall nutrient utilization by the beef and dairy cattle herd. Based on this rationale, we hypothesized that incubation of a Bacillus-based DFM would improve nutrient digestibility of feedstuffs often fed to ruminants. Therefore, our objective was to evaluate the effects of a Bacillus-based DFM on in vitro nutrient digestibility of different single feedstuffs. Six individual feedstuffs were sampled from China and South Africa and used herein. Feedstuffs were incubated or not (CON) with a Bacillus-based DFM (DFM; BOVACILLUS; B. licheniformis and B. subtilis; 3.2 × 109 CFU/gram; Chr. Hansen A/S., Hørsholm, Denmark) over a 48-h in vitro period. The dose of DFM was adjusted to the volume of the flasks being used and to represent the commercial dose of 3 grams/head per day (9.6 × 109 CFU/head). In vitro gas production, dry matter (DM), and neutral detergent fiber (NDF) digestibility were evaluated at 24 and 48 h. Data were analyzed using PROC MIXED of SAS (version 9.4). Mean total in vitro gas production increased by 5.1 and 6.5% when DFM was incubated at 24 and 48 h, respectively (P < 0.01). At 24 h, NDF digestibility was 12.6% greater for DFM-treated feedstuffs vs. CON (P = 0.02; 27.7 vs. 24.6% for DFM and CON, respectively), but no effects were observed on DM digestibility (P = 0.26). Conversely, 48-h DM and NDF digestibility were greater for DFM vs. CON (P ≤ 0.05), with improvements that were in the order of 3.7 and 15.1%, respectively. In conclusion, we observed greater in vitro fiber degradability and gas production of feedstuffs collected from China and South Africa over a 48-h period when the DFM BOVACILLUS was added at a dose representative of 9.6 × 109 CFU per head. Greater improvements in fiber degradability are likely due to the enzymes produced by the DFM BOVACILLUS.

PSIII-28 A Novel Direct-Fed Microbial Supports in Vitro Intestinal Integrity Upon Clostridium Perfringens Challenge

Abstract Gastrointestinal pathogens cause productive, health, welfare, and financial losses to the beef cattle herd. Among these pathogens, Clostridium perfringens type A is of interest given its prevalence, negative effects on intestinal health, and subsequent losses caused in beef animals. Based on this rationale, we hypothesized that a novel direct-fed microbial (DFM) formulation would support the gut barrier integrity upon a challenge with C. perfringens type A. Therefore, our objective was to evaluate how a novel DFM can support the in vitro integrity of intestinal epithelial cell monolayers exposed to C. perfringens type A. Human cancer-derived epithelial intestinal Caco-2 cell monolayers were seeded in transwells for approximately 20 days. A DFM mixture containing Lactobacillus animalis, Propionibacterium freudenreichii, Bacillus licheniformis, and B. subtilis (BOVAMINE DEFEND Plus; Chr. Hansen A/S, Hørsholm, Denmark) was then administered to the apical side of the cell monolayers at 1.0 × 108 CFU/transwell. Then, C. perfringens type A (ATCC #13124) was added at 2.8 × 107 CFU/transwell. Transepithelial electrical resistance (TEER) was measured over a 16-h period, after which area under the curve (AUC) was calculated. By itself, C. perfringens type A led to a TEER decrease that reached its lowest levels at 6.5 h post-pathogen administration. Overall mean decrease in TEER was in the order of 19.3% when compared with control cells. The DFM mixture supported the integrity of the intestinal cell monolayers both with and without the C. perfringens type A challenge, improving AUC by 24.5 and 19.1%, respectively, when compared with non-challenged control cells. In comparison with the negative control cells (C. perfringens-treated), improvements on AUC ranged from 45.6 to 39.4% vs. DFM and DFM + pathogen. In conclusion, these data support our hypothesis that a DFM mixture containing L. animalis, P. freudenreichii, B. licheniformis, and B. subtilis (BOVAMINE DEFEND Plus) supports the gut barrier integrity with or without the pathogenic challenge.

Evaluation of anthelmintic resistance in Oklahoma beef cattle herds and assessment of composite sampling for herd level fecal egg count reduction testing

Beef cow-calf producers submitted fecal samples for fecal egg count reduction (FECR) tests. Anthelmintic administration practices were not controlled, and producers were encouraged to follow standard procedures for each herd. Fecal egg counts (FEC) were determined using the Wisconsin method with alimit of detection of 1 egg per gram (EPG). Inclusion criteria included a pretreatment FEC of 25 EPG. A FECR of ≤ 90% was considered indicative of resistance. Seventeen herds submitted a total of 19 sample sets. All major classes of anthelmintics were represented except for levamisole. Injectable, pour-onand oral as well as original label and generic products were represented. Sample sets from 3 herds were excluded from the final analysis based on inadequate pretreatment FEC. Of the 16 sample sets included in the final analysis, 13 exhibited resistance based on the arithmetic mean of individual FECR tests (FECRT). In addition to individual FEC, composite samples for each herd were created using 1 gram of feces from each animal. Four grams of each composite sample were used to determine a composite FEC. Composite samples from 13 herds were included in the final analysis and 11 of 13 exhibited resistance. There was complete agreement between the individual and composite samples for the detection of resistance. Based on the results of this small survey, apparent anthelmintic resistance appears to be widespread in beef cow-calf herds in Oklahoma. Composite sampling appears to be an effectivemethod for detection of herd level resistance.

PSVIII-29 Nutritional Epigenetic Modifications in Beef Cattle

Abstract Nutrition of the beef cow during pregnancy influences fetal development and potential changes in phenotype. On average 9 to 10% of the beef cattle herd are below the optimal body condition score of 2.5/5 at both pre-breeding and pregnancy tests, indicating potential nutritional stress during gestation. Epigenetic modifications are reported to regulate the changes in phenotype due to maternal nutrition during gestation. Our objective was to evaluate the influence of maternal nutrition during gestation on possible epigenetic mechanisms regulating development and biological function in Longissimus dorsi (LD) and Semimembranosus (SM) muscles, and liver (LV) at slaughter in steer progeny born from dams fed two different planes of nutrition during gestation. We also wanted to explore if the genetic potential of the offspring for residual feed intake (RFI) would interact with prenatal maternal diet to have differential effects on these epigenetic mechanisms. Purebred Angus steer calves (n = 23) were born from dams which were fed a diet formulated for an average daily gain (ADG) of either 0.5 or 0.7 kg/d from 30 to 150 days of gestation. Mating was designed so that calves were born from parents with differential genetic potential for high or low RFI. Calves were raised together as per normal industry standards and fed to be slaughtered as finished steers at approximately 512.1 ± 10.1 days of age. One approximately 10 g sample each of LV, LD, and SM muscles was aseptically collected within 30 to 45 min post-mortem and snap frozen in liquid nitrogen and subsequently stored at -80°C. Both DNA and RNA were isolated from the tissue samples and investigated for differences in methylation and gene expression, respectively. Fifteen potentially differently methylated regions (DMRs) in the DNA were measured using EpiTYPER MassARRAY technology, while expression of genes corresponding to the potential DMRs was measured by the nCounter Element Tagset by NanoString technologies. Average methylation across each DMR as well as gene expression within each tissue was profiled using principal component analyses (PCA). Distinct clustering was seen within both DNA methylation and gene expression PCAs such that the two muscles were clustered together and were separate from DNA methylation and gene expression measured in LV, representing expected functional variation due to tissue type. Between LD and SM, methylation patterns in the two muscles overlap, while there is much less overlap in gene expression patterns. This implies that the methylation pattern between the two muscle types is relatively similar compared with their patterns in gene expression, and that smaller differences in DNA methylation may lead to relatively larger differences in gene expression. These analyses are an important first step to interrogate the quality of our data that will be further analyzed for responses to maternal diet treatment and selection for genetic potential for RFI.

159 Design and Development Mechanics of a Random Forest-Based Decision-Tree Model for Sub-Acute Rumen Acidosis Management in Feedlots

Abstract Sub-acute rumen acidosis (SARA) is a ruminal digestive disorder with a prevalence of 24 to 30% in United States-based feedlots and is responsible for a lost economic opportunity of approximately $1 billion annually. Our objective for this study was to develop a decision tool which feedlot decision-makers could use to make routine managemental interventions that can mitigate the prevalence of SARA. The continuous reduction in rumen pH (pH < 5.6) is the primary causative factor that triggers its onset. However, this prolonged lower rumen pH results from the interaction between multiple other etiological factors. We developed a random forest-based decision tree prediction tool which used seventeen plausible etiological factors, which we broadly classified under four categories, namely 1) animal factors, 2) nutritional factors, 3) environmental factors, and 4) management factors (Table 1), to predict the probability of SARA in a typical US feedlot. A synthetic dataset of 100 observations was created based on a survey conducted among subject matter experts, including ruminant nutritionists, epidemiologists, and decision modelers to chart out the alleged relationship between the above seventeen etiological factors and the probability of a beef cattle population contracting SARA. The random forest model (R, 2021) was used to train as well as test the boot-strapped (80:20 split) synthetic dataset. Ability of random forest to limit overfitting without substantially increasing error due to bias contributed to the high positive predictive value (84%) of the model. Our results indicated that beef yearling cattle with mild temperament, with a rumen pH maintained above 5.6, while being fed three or more times a day, for more than 150 days on concentrate feed, with a stocking density greater than 7 m2, with excellent preconditioning, fed either sorghum or oats which are tempered with a physically effective fiber of 15% and above, under ambient temperature and humidity, along with the feeding of prebiotics, probiotics and ionophores had the least probability to contract SARA. In conclusion, our model can be used by feedlot decision modelers to test different permutations and combinations of these seventeen etiological factors customized to their respective operations to predict the probability of SARA in their herd. Future studies will improve the accuracy of the model by training it on more robust epidemiological datasets sourced from beef herds located in multiple geographic regions.

144 Using Digital Twin Simulations to Optimize Genetic Selection in an Admixed Beef Herd

Abstract Polled cattle, or those that are naturally hornless, are highly advantageous from both an economic and animal welfare perspective. While there are a number of different mutations that result in a polled phenotype, a duplication on bovine chromosome 1, referred to as the Celtic mutation, is the most common within beef cattle. Tropically adapted beef cattle typically have some degree of indicine influence, which are all naturally horned breeds. Polled genes must therefore be introgressed into tropically adapted cattle from naturally polled breeds, such as Angus, carrier of the Celtic mutation. However, Angus are not as well suited for hot, humid climates and introgression cannot happen at the expense of productivity or adaptation. Therefore, strategies must be developed to balance the introgression of poll alleles into a population with continued genetic improvement for economically important traits. This study utilized a privately owned, commercial population of admixed cattle to address this challenge. These cattle (n = ~3,000; single year cohort) were previously genotyped and SNP effects were estimated for heifer pregnancy as part of the internal genetic evaluation of the private enterprise. Management and selection of male and female replacements were modelled using actual production parameters in a digital twin framework. Four different breeding systems, multi-sire natural service, artificial insemination, and invitro fertilization collecting either five or 10 oocytes, were modelled and compared with account for differences in selection intensity. Selection index weighting of poll vs heifer pregnancy was modelled in eight different combinations. Genetic crosses were then simulated using the real genotypes in the genomicSimulation package in R for 5, 10, and 30 years of crosses to evaluate long and short-term consequences. We found that this approach of combining digital twin modelling with simulated crosses can be used to identify the selection strategy that should be applied to optimally balance selection for poll and economically important traits, such as fertility. This modelling approach provides a framework that may be customized to fit specific production parameters or genetic populations representing individual operations. More generally, this particular study used cattle and management practices representative of the northern Australian beef industry, and may be used as a reference for producers in that production system of strategies for increasing the rate of polled animals in their herds. Furthermore, this approach may be applied to the selection for or against other single gene traits, such as many genetic disorders. The USDA is an equal opportunity provider and employer.

PSIX-29 Needs Assessment for the Use of Genomic Selection Within the Commercial Beef Sector

Abstract Although purebred cattle producers have had genomic EPDs for over a decade, crossbred commercial beef cattle producers have not had the opportunity to use genomic selection for improvement of their cattle. This study aimed to identify what is needed to facilitate the adoption of genomic selection in crossbred beef herds through a survey of beef cattle associations in the western United States. Surveys were distributed electronically through state cattlemen’s associations in Arizona, Idaho, Nevada, Utah, Washington and Wyoming. Nineteen individuals completed the survey representing predominantly cow/calf operations (68%), followed by stockers (9%), feedlots (5%), raising of replacement heifers (5%), and a seedstock producer (5%). Most beef producers (74%) had heard about genomic selection, but only 26% had utilized genomic selection. Of those who had previously used genomic selection, most (60%) were cow/calf producers. Those using genomic selection had done so to identify superior animals (33%), to select replacement heifers (25%) or to identify calf parentage (17%). The use of genomic selection to reduce or manage financial risk or to choose AI bulls for mating selection could expand the value of genomic selection for the beef producer while increasing the rate of genetic improvement in their herd. Interests and concerns regarding genomic selection were also identified, which can be utilized to identify areas of extension and outreach that need to be improved for the technology to be adopted and used more effectively. Key topics needed for genomic selection to be adopted were confirming that genomic selection resulted in a positive return on investment, being able to confidently interpret genomic EPDs, learning how to fully use the genomic EPD results, and information regarding the accuracy of the genomic selection results. The potential for genomic selection within the beef industry is immense, and this survey confirmed that extension programs on genomic selection use have the opportunity to be beneficial to commercial beef producers throughout the industry to improve the genetics of their herds while reducing their financial risk.

Candidate genes for longitudinal traits under sequential sampling in beef cattle.

Both the measurement age of a longitudinal trait and the common pre-sampling procedures used in beef cattle herds may affect the identification of a functional candidate gene (FCG) that is potentially associated with a trait. To identify the FCG that takes part in the genetic control of body weight at five different ages in a beef cattle population with and without sequential sampling, the animals were weighed at different measurement events, around 330, 385, 440, 495 and 550 days old. Genetic parameters were estimated for body weight at each age using a single trait (STM) and a random regression model (RRM). In addition, two different databases were used to estimate the genetic parameters: the first (DB100) was formed by all animals that were weighed in the five measurement events, and the second (DB70) has records of the same population, considering that 70% of the heaviest animals were selected after each measurement event. For DB100, genome-wide association studies (GWAS) were performed with 21,667 SNP markers to identify genomic windows that explained at least 1% of the genetic variance. Additionally, prioritization analyses were performed and FCGs were selected. We associated seven different FCGs with body weight at different ages. Among them, the gene DUSP10 was suggested as FCG in all five ages evaluated. Genetic parameters estimated for body weight using DB100 were similar when STM and RRM were applied. However, when DB70 was used as phenotypic data, there were differences between the two models. When the STM was applied, there were differences between the genetic parameters estimated for body weight when DB100 or DB70 were used as sources of phenotypes, but not for the estimates obtained with RRM. The importance of each gene for animal growth can change at different ages, and different genes may be more relevant to body weight at each different growth stage for beef cattle. Besides, sequential sampling can affect the GWAS results of a longitudinal trait. The age of the animal when a longitudinal trait is measured and pre-sampling can also contribute to inconsistencies in GWAS results for body weight in beef cattle, depending on the time when that data were collected, and consequently on the identification of FCG between studies, even when models that consider a covariance structure are used.

The first molecular characterization and phylogenetic analysis of bovine papular stomatitis virus in Iran

Bovine papular stomatitis (BPS) generally is a mild viral disease caused by the Bovine papular stomatitis virus (BPSV) belonging to the genus Parapoxvirus (PPV). This study aimed to perform the first molecular characterization and phylogenetic analysis of BPSV in beef calves in Iran. Clinical examinations were carried out on four beef cattle herds in West Azerbaijan province, which had experienced outbreaks of papular lesions. Fifty swab samples were collected from the papular lesions on the muzzle, lips, and oral cavity of affected calves, and after viral DNA extraction, they were subjected to polymerase chain reaction (PCR). The results of PCR confirmed the presence of BPSV in all calves with clinical symptoms. The partial B2L gene was sequenced based on nucleotides, and phylogenetic analysis was performed using MEGA 11.0.13. The analysis revealed that BPSV isolates from beef calves in Iran formed two clades. Clade 1 exhibited similarities to the isolates from Finland, Japan, and Georgia, while Clade 2 was similar to the Zambian isolates. These findings indicate the presence of genetic diversity and potential variability within the virus population. Further studies with larger sample sizes and diverse geographic regions will increase the resolution of the phylogenetic tree and contribute to a comprehensive understanding of how BPSV circulates in the country.