Recipient Organization
OKLAHOMA STATE UNIVERSITY
(N/A)
STILLWATER,OK 74078
Performing Department
Animal & Food Sciences
Non Technical Summary
There is speculation that selection for 'economic' traits (growth, milk, and carcass traits) results in reduced immune function and increased susceptibility to disease, with morbidity occurring later in the finishing period than typical morbidity patterns.Hypothesis:Focused selection of beef cattle for economic traits in elite herds has reduced robustness and resilience to stressors in the beef production chain.Objectives:1. Determine the effects of selection focused on economic traits on phenotypic expression of immune competence and stress responsiveness of growing steers.2. Examine the impacts of seasonal changes in climate and dietary resources provided to the dam on phenotypic expression of immune competence and stress responsiveness of their offspring.We aim to determine the effects of selection of moderate or extreme genetics for weaning and yearling weight, and milk yield in the cow/calf sector on the feed intake, feed efficiency, growth performance, and carcass characteristics of steers; and characterize the stress and immune responsiveness, behavior, and temperament and thus subsequent robustness to stressors and health challenges.The results of this project will provide a foundation for further investigations into the effects of genetic selection on animal health and wellbeing and offer a biological basis for alternate selection criteria and genetic-based tools for health and welfare-based selection.
Animal Health Component
30%
Research Effort Categories
Basic
70%
Applied
30%
Developmental
(N/A)
Goals / Objectives
Long-Term Goals: The results of this project will provide a foundation for further investigations into the effects of genetic selection for economic traits on animal health and wellbeing and offer a biological basis for alternate selection criteria and genetic-based tools for health and welfare-based selection.Objectives:Determine the effects of selection focused on economic traits on phenotypic expression of immune competence and stress responsiveness of growing steers.Examine the impacts of seasonal changes in climate and dietary resources provided to the dam on phenotypic expression of immune competence and stress responsiveness of their offspring.
Project Methods
Experimental populations: This research will use steer calves produced by the Oklahoma State University Range Cattle Research Center. The cowherds of approximately 200 fall calving (North Range) and 200 spring calving (South Range) cowsbeing bred via artificial insemination to Angus sires selected for moderate (50th percentile) vs. high (1st percentile) weaning weight and yearling weight EPDs and milk EPD (95th vs. 10th percentile) for both fall and spring calving herds in a 2 x 2 x 2 factorial arrangement.Each herd is expected to produce 60 AI sired steers for the post-weaning experiment; this should result in 15 calves for each selection criteria (i.e., 15 high growth/high milk; 15 high growth/low milk; 15 moderate growth/high milk; and 15 moderate growth/low milk). Tissue samples will be collected from all calves for genotyping to confirm parentage and analysis of growth, milk, carcass traits, and disposition genotypes to rank these traits. The effect of breeding selection and nutritional and environmental differences during prenatal, neonatal, and pre-weaning periods on gene expression for growth, carcass, and immune traits will also be determined.Animal management and sampling: Calves are both fall (bred to calve in September and October) and spring (bred to calve in March and April) calving but use similar management schedules. Calves from both calving seasons will be used through two entire production cycles, from weaning through finishing beginning with the 2022 calving seasons and culminating with the slaughter and carcass data collection of the 2023 calf crop in September 2024 (Spring calves) and February 2025 (Fall calves). Preweaning:Within 24-hours of birth, blood will be collected from a subset of cows and their steer calves for cortisol and immunity analysis. At 3 to 4 months of age calves will be weighed, ear notch samples collected for genotyping, administered with a multivalent modified live vaccine for (IBR, BVD I and II, PI3, and BRSV) and blood collected from steer calves for further analysis to characterize passive immune transfer at calving and cortisol levels. Chute scores and exit velocity will be collected at this time to characterize disposition and temperament.Preconditioning: Calves will be weaned at 6 to 7 months of age.Steers will be removed from the dam and kept in pens located at the respective Range Cattle Research Center Unit as a single group and offered free-choice long-stem hay and a weaning supplement fed at 2.5 kg/calf daily designed to provide protein and minerals to meet the requirements of a calf gaining 1 kg/day. Fecal and blood samples will be collected at weaning and on day 28. Sera and fecal samples will be analyzed for cortisol.Average daily gain, morbidity, mortality, and treatment cost will be evaluated for the 60-day preconditioning phase.Finishing phase: Following the 60-day preconditioning phase, steers will be transported to the OSU Willard Sparks Beef Research Center (WSBRC) for finishing. The proposed study will utilize technology (Insentec Intake System) which measures feed and water intake on an individual basis without physical barriers that isolate animals from feed and water sources.Average daily gain, morbidity, mortality, and treatment cost will be evaluated for the finishing phase. Average daily gain, feed dry matter intake, and feed efficiency will be tracked during the Insentec feed intake determination period. Calves will be monitored daily for health and wellbeing by trained personnel.Genotyping: Ear notch will be collected from steers that will be potentially enrolled in the study based on birthdate (close to the due date from artificial insemination) in order to ensure parentage is by the intended sire.We will also explore relationships between commercially available genomic marker scores (Neogen Corp., Lansing, MI) for RFI, milk, and average daily gain with the phenotypic expression of those traits for the sire selection criteria groups and season of birth as well as with the cellular and antibody-based immunity traits.Immune phenotype analysis: Blood will be collected for whole blood and sera analysis at 5-time points: branding (3-4 months of age), weaning, and 14 days post-weaning during the preconditioning phase and following entry in the feedlot on days 0 and 28 of finishing (60 and 88 days post-weaning, respectively), corresponding with expected stress events of weaning and dietary changes.Sera will be tested for neutralizing antibodies at the SDSU Serology Laboratory for bovine viral diarrhea virus 1 (BVDV1), bovine herpesvirus-1 (BHV-1), and bovine respiratory syncytial virus (BRSV), to identify differences in titer response to sire selection criteria. Cell-mediated immune response will also be measured through sera cytokine and immunoglobulin analysis.Whole blood will be used to determine differential immune cell counts, neutrophil, and NK cell function, and lymphocyte proliferation. Whole bloodsamples willbe processed and analyzedfor phenotypicand functional assessment of innate (i.e., NK cytotoxicity) and adaptive immunity (i.e., T and B cell proliferation)Fecal and serum samples will be collected from all steers at 4 time-points (Figure 3): branding (3-4 months of age), weaning, and 14 days post-weaning during the preconditioning phase and following entry in the feedlot on days 0 and 28 of finishing (60 and 88 days post-weaning, respectively). These samples will be analyzed for fecal and serum cortisol and serum Corticosterone Globulin Binding Protein.Delay-type hypersensitivity reaction to multivalent (7-way) clostridial vaccine administered at weaning subcutaneously will be assessed on all animals by intradermal injection of the same vaccine to determine cell-mediated immune response day 14 post-weaning (Hine et al., 2019). First, double skinfold thickness will be measured using calipers at the caudal tail fold injection site to provide a baseline. Clostridial vaccine (right-hand side) 100 µL and 100 µL saline (control, left-hand side) will be injected intradermally using an insulin syringe with a 0.95 cm × 26g needle on alternating sides of the caudal tail fold. At 48-hour post-injection, the change in double skinfold thickness will be measured. The magnitude of change in double skinfold thickness will be calculated as:Log(double skinfold thickness at reaction site/double skinfold thickness at control site)Disposition and temperament: Both exit velocity and chute scores have been shown to accurately assess cattle temperament, both will be used in the proposed research. Chute scores are based upon observations of cattle behavior while entering and exiting, or restrained, in a squeeze chute. Chute scores are assigned on a scale of 1-to-6, increasing in number as cattle aggression increases. Cattle behavior such as head jerking, tail flicking, jumping, bellowing, and general agitation are observed while an animal enters the squeeze chute, is restrained, and exits the chute. The score is a type of summation of the individual's behavior during the overall squeeze chute experience.Metabolite, Metabolomics, and Proteomics Analysis: This analysis will be conducted to define metabolic pathways and gene expression altered by both genetic selection of the sire and nutrient restrictions and environmental conditions during gestation and preweaning. On day 14 of finishing (88-days post-weaning) and after the 70-day Insentec feeding evaluation (158-days post-weaning) blood will be collected for analysis of metabolites and muscle and liver biopsies will be collected for metabolomics and proteomics.