2012 Annual Report
1)evaluate the influence of steroid implants on stress hormones, fecal shedding of E. coli O157:H7 and Salmonella, and growth and carcass traits in weaned, crossbred calves and.
2)determine if differences within prolactin, heat-stress protein (HSP), and lactate dehydrogenase (LDH) genes are related to stress hormone concentrations, fecal shedding of pathogens, or steer growth and carcass traits. Weaned, crossbred bull calves (n = 80; approximately 550 lbs) were purchased from local auctions, held at a private farm for 14 days, and delivered to the USDA/ARS Dale Bumpers Small Farms Research Center research farm in Booneville, Arkansas. While on the private farm, calves were castrated (n = 60) or left intact (n = 20), dewormed, and vaccinated. On day 0, 14, 15, 16 of the study (at the private farm), blood and fecal samples were collected from each calf; calves received an estradiol implant, a trenbolone acetate implant, or no implant (n = 25/treatment). Intact calves were not implanted until after castration on day 16. Tissue samples (ear tag system) were collected for a genotyping study. On Day 14, calves underwent shipping stress (driven approximately 40 miles) to and from the ARS research station. Calves grazed bermudagrass pastures and were supplemented with grain. Calves will graze for approximately 150 days (currently grazing as of August). At that time they will be sampled (fecal and blood) and sent to a feed yard. Following the feedyard phase, carcass data will be collected.