|Vander ley, B|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/7/2011
Publication Date: 6/1/2012
Publication URL: http://jas.fass.org/content/90/6/1972
Citation: Richeson, J.T., Kegley, E.B., Powell, J.G., Vander Ley, B.L., Ridpath, J.F. 2012. Weaning management of newly received beef calves with or without continuous exposure to a persistently infected bovine viral diarrhea virus pen mate: Effects on health, performance, bovine viral diarrhea virus titers, and peripheral blood leukocytes. Journal of Animal Science. 90:1972-1985. Interpretive Summary: Preconditioning, by definition, is a vaccination, nutrition, and management program designed to prepare young cattle to withstand the stress associated with weaning and shipment to a feedlot. This is accomplished by exposing the calf to the stresses of weaning, vaccination, and other common processing procedures such as castration, dehorning, and treatment with systemic parasiticides, well in advance of its entry into the feedlot. In contrast, most calves purchased at the auction market, undergo these processing procedure immediately before sale or upon entry into the feedlot. The goal of this study was to compare performance of preconditioned calves (PC) and auction market calves (AM) in feedlots in the presence and absence of a virus. The exposure to virus was done by penning calves with other calves that were persistently infected with a virus known of bovine viral diarrhea virus. The results of the study indicate that PC calves gain weight faster and require fewer antibiotic treatments. The performance of both PC and AM calves were worse in the presence of virus. However, the negative effect of virus was stronger with AM calves as they required more antibiotic treatments and were more likely to develop chronic health problems. These results suggest that preconditioning calves results in healthier animals, that gain weight faster, are more resistant to disease and require less antibiotic use. The take home message is that preconditioning calves increases profitability and reduces use of antibiotics.
Technical Abstract: Exposure to animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) results in immunomodulation that may have health and growth consequences; however, effects may differ in low-risk, preconditioned (PC) vs. high-risk, auction market (AM) cattle. Our objective was to compare health and performance of PC or AM management systems, with (PI) or without (CON) presence of a PI-BVDV pen mate using a 2 × 2 factorial arrangement. Four shipment blocks of crossbred PC steers (n = 236) from 3 ranch-origins were selected randomly, weaned, dewormed, vaccinated, tested for PI-BVDV, and kept on the ranch for greater than or equal to 42 d. Subsequently, PC steers were transported to a stocker receiving unit (RU), weighed (251 ± 2 kg), bled, stratified by d -1 BW, and assigned randomly to treatment (PCPI or PCCON) with no additional processing. Simultaneously, 4 blocks of crossbred AM calves (n = 292) were assembled from regional auction markets and transported to the RU ± 36 h from PC arrival. The AM calves were weighed (245 ± 1.3 kg), stratified by gender and d -1 BW, processed under the same regimen used for PC steers at their origin ranch except bull calves were castrated, then assigned randomly to treatment (AMPI or AMCON). Treatment pens (0.45 ha) were arranged spatially such that PI did not have fence-line or water source contact with CON. Calves were fed identically and followed the same antibiotic treatment protocol. Daily gain for the entire 42-d receiving trial was greater (P < 0.001) for PC (1.2 kg) compared to AM (0.85 kg). There was an exposure effect (P = 0.002) on ADG from d 28 to 42; CON gained 1.12 kg vs. 0.90 kg for PI cohort. Morbidity was markedly greater (P < 0.001) in AM (70%) vs. PC (7%), resulting (P < 0.001) in an antibiotic treatment cost of $20.52 and $2.48/animal, respectively. Treatment with a third antibiotic occurred more often (P = 0.04) for PI cohort and the percentage of chronically ill cattle were greatest (P = 0.06) for AMPI. Upon arrival, BVDV type 1a, 1b, and 2a titers were greater for PC (treatment x day, P < 0.001), and the percentage seropositive to BVDV type 1a on d 0 was 100% for PC vs. 23% in AM. Platelets increased transiently 37 (P < 0.001), with greater platelets observed in AM (P < 0.001). Results indicate that PC calves gain faster and require fewer antibiotic treatments. Exposure to PI reduced gain from d 28 to 42, increased the number of calves requiring a third antibiotic treatment, and increased chronically ill cattle for AM.