INTERVENTION STRATEGIES TO CONTROL VIRAL DISEASES OF CATTLE
Location: Ruminant Diseases and Immunology Research Unit
Title: Weaning management of newly received beef calves with or without exposure to a persistently infected bovine viral diarrhea virus type 1b calf: Effects on health, performance, BVDV type 1a titers, and circulating leukocytes
| Richeson, J - |
| Kegley, E - |
| Powell, J - |
| Vander Ley, Brian |
Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: November 15, 2010
Publication Date: February 6, 2011
Citation: Richeson, J.T., Kegley, E.B., Powell, J.G., Vander Ley, B.L., Ridpath, J.F. 2011. Weaning management of newly received beef calves with or without exposure to a persistently infected bovine viral diarrhea virus type 1b calf: Effects on health, performance, bovine viral diarrhea virus type 1a titers, and circulating leukocytes [abstract]. In: Proceedings of the American Society of Animal Science, Southern Section Meeting, February 6-8, 2011, Corpus Christi, Texas. Journal of Animal Science. 89(E-Suppl. 2):20-21. Available: http://www.asas.org/abstracts/ASAS_2011_Sect_ABS_E-Supplement-2.pdf.
Bovine viral diarrhea virus (BVDV) is a major culprit in the development of bovine respiratory disease (BRD) either directly via acute clinical illness or indirect effects of immunosuppression. Calves born persistently infected (PI) with BVDV are the primary transmission source of the virus; however, consequences of exposure to a PI-BVDV calf in a single-source, preconditioned (PC) vs. commingled, auction market (AM) cohorts may differ because these distinct management groups may possess different physiological and immunological circumstances. Our objective was to compare treatments of PC or AM origin, with (PI) or without (CON) continuous exposure to PI-BVDV type 1b challenge in a 2 x 2 factorial arrangement to evaluate main effects of source, exposure, and their interaction on health parameters and growth performance during a 42-d receiving trial. Four sets (block) of crossbred PC steers (n = 236) from 3 ranch-origins were selected randomly, dewormed, administered 5-way respiratory, 7-way clostridial, and Mannheimia haemolytica vaccines, tested for PI-BVDV status, and weaned on the ranch for greater than or equal to 42 d. After the pre-trial weaning phase ended, 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 sets of crossbred AM claves (n = 292) were assembled from regional auction markets for delivery to the RU within 24 h of PC arrival. The AM calves were weighed (245 ± 1.3 kg) and administered identical processing procedures as PC received at their origin ranch; however, bull calves were stratified by gender and d -1 BW, castrated surgically, then AM calves were assigned randomly to treatment (AMPI or AMCON). Treatment pens (0.45 ha) were arranged spatially so 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 from d 0 to 42 was greater (P < 0.001) for PC (1.2 kg) than AM (0.85 kg). There was an exposure effect (P = 0.002) on ADG from d 28 to 42; CON gained 1.12 vs. 0.90 kg for PI. Morbidity rate was markedly greater (P < 0.001) in AM (70%) than PC (7%). Although PI exposure did not affect (P = 0.41) the overall BRD morbidity rate, treatment with a third antibiotic occurred more than often (P = 0.04) for PI-exposed cohorts. A treatment interaction (P = 0.06) was observed for the percentage of chronically ill animals; AMPI had the greatest number of chronically ill calves (7.6%), AMCON was intermediate (1.1%), and PCCON and PCPI were least (0.4 and 0.3%, respectively). A trend (P = 0.10) was observed for PI-exposed calves having an increased antibiotic treatment cost which averaged $12.59 and $10.40/animal for PI and CON treatments, respectively. Within AM calves, PI exposure resulted in an antibiotic treatment cost of $4.06/animal more than CON; this numerical difference being similar to PI-BVDV testing cost/animal. The BVDV type 1a antibody titer levels were greater on d 0 for PC (treatment x day, P < 0.001), and seroconversion to BVDV type 1a on d 0 was 100% for PC vs. 23% in AM. Exposure to PI-BVDV type 1b challenge did not impact (P = 0.98) BVDV type 1a titer levels, which suggests that antigenic differences may exist among these BVDV subgenotype strains. Total leukocytes were greater (P < 0.001) for PC on d 0, 14, and 28. The neutrophil:lymphocyte (N:L) ratio was greater (P < 0.001) for AM on d 14 and 28. Platelet count increased transiently (P < 0.001), with greater platelets observed in AM (P < 0.001). Results of our study indicate that PC steers gain faster and require fewer antibiotic treatments than AM calves because stress is reduced and immunity is improved as evidenced by differences in N:L ratio and on-arrival BVDV type 1a antibody titers. Health consequences of exposure to PI-BVDV challenge may be greater for AM calves because chronically ill cattle were most frequent for AMPI. Furthermore, PI-BVDV exposure reduced ADG from d 28 to 42, perhaps due to an additive affect of continuous immune stimulation resulting in nutrients being preferentially utilized for immune pathways rather than tissue deposition. Preconditioning management practices have long-term implications for health, performance, profitability, and animal well-being.