Evaluation of Immune Response and Performance in Steers of Known Genetic Background Vaccinated and Challenged with Bovine Viral Diarrhea Virus
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This research was directed at investigating the variation in immune response of cattle when administered a known challenge from Bovine Viral Diarrhea Virus (BVDV) following different Bovine Respiratory Disease (BRD) vaccine treatments. Cattle were assigned vaccine treatments with sire and cow family was stratified across treatments to assess the role genetic differences may impact immune function. The same BVDV strain and challenge technique were used in two trials (2008 and 2009) in Angus-sired yearling steers. Data from these two years were analyzed separately because the cattle were managed and fed differently. Blood antibody Immunoglobulin-G (IgG) titers for IBR, BVD Type 1 and BVD Type 2 were higher for cattle in the Killed vaccine group than the MLV or NON vaccinated groups (P < 0.05) in both years. In the 2008 study, average daily gain (ADG) was higher for cattle from the Killed vaccine group (P < 0.05) for the 28 d following BVDV challenge, but no cattle were classified as morbid based on rectal temperature. In the 2009 study, differences in rectal temperatures were observed, and a total of 35 of 93 having over 40.0 degrees C (28 in the first 14 d following challenge). Cattle in the MLV vaccine group had lower overall mean temperatures, with no animals having rectal temperatures over 40 degrees C 14 d following viral challenges. Differences in rectal temperature were also observed due to sire. Differences in feed intake also occurred due to treatment, day, treatment ? day interaction, and maternal-grandsire. The MLV vaccine group maintained more constant levels of intake as compared to Killed and NON vaccinated cattle at days 5 to 12. Although large differences in titers following BVDV challenge were observed, the relationships of this immune response with animal health and performance appears very complex.