Date of Graduation

5-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Animal Science (PhD)

Degree Level

Graduate

Department

Animal Science

Advisor

Elizabeth B. Kegley

Committee Member

Paul A. Beck

Second Committee Member

Gisela F. Erf

Third Committee Member

Keith S. Lusby

Keywords

Biological sciences; Bovine respiratory disease; Bovine viral diarrhea virus; Performance; Precondiitoning

Abstract

A series of experiments were conducted to determine the effects of on-arrival vs. delayed respiratory vaccination and exposure to persistently infected bovine viral diarrhea virus challenge on health, gain performance, and physiological and immunological measurements in newly received stocker cattle. Two experiments evaluated timing (d 0 vs. 14) of respiratory, clostridial, or both vaccinations in newly received stocker calves during stress-induced immunosuppression. In Exp. 1, calves receiving 14-d delayed vaccination of a pentavalent modified-live respiratory virus (MLV) vaccine had greater ADG during the 42-d receiving period and antibody titers against infectious bovine rhinotracheitis on d 42; however, morbidity rate did not differ. In the second study, stress indicated by serum cortisol concentration and neutrophil:lymphocyte ratio was greatest on d 0; nevertheless, no differences in performance or morbidity were observed for vaccination treatments. Both studies provided evidence that on-arrival administration of a pentavalent MLV respiratory vaccine to immunocompromised cattle does not mitigate clinical bovine respiratory disease (BRD) or improve animal performance because the majority of clinical respiratory disease for both studies occurred during the first 14-d and morbidity rate was not different when calves were vaccinated on d 0 vs. 14. A third experiment was performed to determine the effects of weaning management and subsequent exposure to persistently infected (PI) bovine viral diarrhea virus (BVDV) challenge on health, performance, bovine viral diarrhea virus titers, peripheral blood leukocytes, and inflammatory cytokines. The objective was to compare preconditioned (PC) or auction market (AM) origin cattle, with (PI) or without (CON) continuous exposure to PI-BVDV type 1b challenge in a 2 × 2 factorial arrangement to evaluate main effects of management, exposure, and their interaction on health parameters and growth performance during a 42-d receiving trial. Preconditioned calves that were vaccinated, castrated, and weaned at their origin ranch had greater gain performance and reduced BRD morbidity compared to AM calves with unknown history. Furthermore, PC cattle had greater antibody titers to BVDV type 1a on d 0, and neutrophil:lymphocyte ratio and platelet count were lower during the 42-d receiving period. Exposure to PI-BVDV challenge reduced gain from d 28 to 42, perhaps due to an additive effect of continuous immune stimulation resulting in nutrients being preferentially utilized for immune pathways rather than tissue deposition. A treatment interaction 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). Exposure to PI-BVDV challenge increased serum TNF-alpha concentrations, and IFN-gamma concentrations on d 14 and were greatest for AMPI, intermediate for PCPI, and least for AMCON and PCCON. The increased cytokine concentrations associated with PI-BVDV exposure illustrate a more stimulated immune response which has implications for animal health due to taxation of the immune system and growth due to a homeorhetic response in which nutrients may be preferentially shifted towards immune function rather than tissue growth.

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