THE OVERALL USE OF GENETIC AND GENOMIC TECHNOLOGIES FOR BEEF CATTLE SYSTEMS FOR BEEF CATTLE HEALTH IMPROVEMENT

Date

May 2023

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Abstract

As genetic and genomic technology continues to advance within the beef industry, there is an opportunity to improve beef cattle systems. Specifically, this may be achieved by evaluating genetics and environment of beef cattle simultaneously. As such, we conducted two independent experiments to 1) analyze host gene expression upon cattle arrival to a backgrounding system to determine predictive candidate biomarkers and genomic mechanisms related to respiratory disease risk and acquisition, and 2) evaluate production and carcass characteristics from the offspring of cloned sires to determine if meat quality and growth performance are replicable across a generation. In experiment 1, bovine respiratory disease (BRD) remains the leading disease within the U.S. beef cattle industry. Marketing decisions made prior to backgrounding may shift BRD incidence into a different phase of production, and the importance of host gene expression on BRD incidence as it relates to marketing strategy is poorly understood. Our objective was to compare the influence of marketing on host transcriptomes measured on arrival at a backgrounding facility on the subsequent probability of being treated for BRD during a 45-day backgrounding phase. This study, through RNA-Seq analysis of blood samples collected on arrival, evaluated gene expression differences between cattle which experienced a commercial auction setting (AUCTION) versus cattle directly shipped to backgrounding from the cow–calf phase (DIRECT); further analyses were conducted to determine differentially expressed genes (DEGs) between cattle which remained clinically healthy during backgrounding (HEALTHY) versus those that required treatment for clinical BRD within 45 days of arrival (BRD). A profound difference in DEGs (n = 2961) was identified between AUCTION cattle compared to DIRECT cattle, regardless of BRD development; these DEGs encoded for proteins involved in antiviral defense (increased in AUCTION), cell growth regulation (decreased in AUCTION), and inflammatory mediation (decreased in AUCTION). Nine and four DEGs were identified between BRD and HEALTHY cohorts in the AUCTION and DIRECT groups, respectively; DEGs between disease cohorts in the AUCTION group encoded for proteins involved in collagen synthesis and platelet aggregation (increased in HEALTHY). Our work demonstrates the clear influence marketing has on host expression and identified genes and mechanisms which may predict BRD risk. In experiment 2, animal breeding and genetics have shifted significantly over the past several decades. Previously, genetic improvement of beef cattle was largely dependent on visual appearance. While this remains valuable in selecting cattle for breeding, current technology and performance determination contributes to modern genetic improvement strategies. As such, we have continued a unique crossbreeding project beginning with rare carcasses that exhibited a highly desirable yet antagonistic trait which includes being USDA Prime and yield grade 1. Sires (Alpha, Delta and AxG1) were produced and evaluated originally for high quality carcass characteristics, then bred accordingly in the summer of 2020. Our objective was to see if their offspring could replicate similar outcomes and produce quality carcasses and growth characteristics. Here, thirty-five bull (n=24) and heifer (n=11) calf offspring were fed a commercial feedlot ration at the Palo Duro Consultation, Research & Feedlot in Canyon, TX for 68 days. Parentage results were tested to confirm sire, followed by weight gain, feed intake, and carcass ultrasound data collections. Significant differences were found (P<.05) for entire average daily gain and average intake, rib fat and backfat, and ribeye area and percent intramuscular fat for both SIRE and SEX. Spearmen’s Rank correlations were found of (P<.05), with a coefficient of 0.59 for ADG and average intake, 0.42 for RF and BF both for SIRE. Spearmen’s rank correlations for SEX found no significance for ADG and average intake but when evaluating RF and BF between sex on d68 significance was found (P< .05) with a coefficient of 0.39. Our results can help confirm the relationship between larger RF and BF with weight gain, as well as the relationship between carcass quality in the specific sex of beef cattle.

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Keywords

Agriculture, Animal Pathology, Biology, Animal Physiology

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