PSI-6 Effects of rest period prior to processing on vaccine response and blood metabolites in feedlot heifers

Abstract It is common for feedyards to rest cattle after transport and prior to administration of their receiving vaccinations in an attempt to minimize transport stress and optimize vaccine efficacy and subsequent growth and performance. This study aimed to test how time of rest after feedlot heifer arrival impacts vaccine titer and blood metabolites indicating cattle health. Eighty mixed-breed heifers (250 ± 4.2 kg BW) were purchased at live auction in Oklahoma City, OK and transported to the Kansas State University in Manhattan. Heifers were allotted in a completely randomized design to one of four treatments processed at 0, 6, 24, or 48 hours after arrival. At the time of processing (d 0) and again on d 35, serum samples were collected and analyzed for infectious bovine rhinotrachitis (IBR) titer, large animal chemistry panel, and hepatic profile by the Kansas State Veterinary Diagnostic Laboratory. There were time × treatment interactions (P < 0.02) for serum IBR titer, glucose, urea nitrogen, and bicarbonate. Specifically, heifers had greater (P < 0.05) IBR titer on d 35 than d 0, as expected because they were vaccinated upon arrival. Upon arrival, cattle held for 48 hours prior to processing had significantly greater (P < 0.05) glucose than those held for 24 hours (108 vs. 68 mg/dL, respectively), with no differences in processing treatment by d 35. Urea nitrogen levels in cattle held for 6, 24, or 48 hr prior to processing were greater (P < 0.05) than those held for 0 hours on d 0 or for any length of time by d 35. Finally, cattle held for 0 or 48 hr prior to processing had lower (P < 0.05) bicarbonate levels on d 0 than those held for 6 or 24 hours by d 35. These data show that while initial rest may be helpful to normalize blood metabolites, cattle should be placed within 24 hours of arrival. However, most blood metabolite levels normalize within 35 days.