Date of Award
Master of Science
James M. Reecy
Animal health is a major concern in today's livestock industry. Not only is animal illness costly, but it also affects all aspects of the industry from the cow calf producer to the feedlot operator. Bovine respiratory disease (BRD) has large economic ramifications to the beef industry. Bovine respiratory disease has been characterized an interaction between environment, stress, and infectious pathogens. Preventative methods such as vaccination have been used to minimize the repercussions that have been associated with BRD. While vaccination has been used as a preventative method, it is only effective if an immune response is mounted to the specific antigen present in the vaccine. The objectives of the studies were three fold: 1) to identify sources of fixed effects that influence maternal antibody levels and maternal antibody decay, 2) to identify the environmental and management factors that influence antibody response to BVDV2 vaccine, and 3) to evaluate effects of BVDV2 antibody response on body composition ultrasound, performance, and carcass quality traits. In these studies, immune response was measured by antibody response to bovine viral diarrhea virus type 2 (BVDV2). With respect to objectives 1 and 2: calf age nested within birth year season and dam age significantly (P<0.05) affected all passively-acquired maternal antibody level and vaccine response traits evaluated. The amount of circulating passively-acquired maternal antibodies present at the time of vaccination has a significant (P<0.05) effect on antibody response to vaccination for final antibody level and initial, booster, and overall response. Calves that were weaned at the initial vaccination had significantly (P<0.05) higher final antibody levels and response to vaccination compared to animals weaned at the booster vaccination. In order to mount an antibody response to vaccination, maternal antibodies in circulation need to be below a given threshold.
With respect to objective 3, increased final antibody level significantly (P<0.05) increased yearling weight and subcutaneous fat over the rump. The interaction between final antibody level and wean stress treatment had a significant (P<0.05) effect on Warner-Bratzler shear force (WBSF) and pH. While, overall antibody response by wean stress interaction had a significant (P<0.05) effect on ADG and pH. Animals weaned at initial vaccination had significantly (P<0.05) higher intramuscular fat and harvest weights than animals weaned at the booster vaccination, with no significant (P<0.05) effects from final antibody level or overall response. Animals that were weaned at the initial vaccination with high response level had significantly (P<0.05) higher ADG, harvest height, and HCW compared to animals with a high response level weaned at the booster vaccination. Increased antibody response did not significantly (P<0.05) decrease performance or carcass quality in finished cattle. Overall increased antibody response to vaccination did not jeopardize performance or carcass quality. Decreased maternal antibodies at vaccination and weaning calves at the initial vaccination allowed for greater response to vaccination. Additionally, animals weaned at the initial vaccination and had high response to the vaccination had increased performance. Taken together these results, provide needed information for producers so that they can maximize the effectiveness of vaccination, which should help them to better control BRD.
Erika Diane Downey
Downey, Erika Diane, "Evaluation of environmental effects on bovine viral diarrhea virus type 2 (BVDV2) antibody levels and response to BVDV2 vaccinations in Angus calves" (2011). Graduate Theses and Dissertations. 10445.