ARS | Publication request: The kinetics of white blood cell counts during vaccination against bovine respiratory disease pathogens and their correlations with lung lesions, diagnosis and average daily gain

Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 26, 2012
Publication Date: N/A

Technical Abstract: Bovine Respiratory Disease (BRD) is the most common disease within US feedlots. Infection can result in morbidity, mortality and reduced average daily gain. The discovery of cheap and reliable methods of prediction and/or protection would be highly advantageous to both breeders and farmers. Cattle (2182) were vaccinated against common viral and bacterial pathogens of BRD. Two blood samples were collected; during booster vaccination and 21d later, enabling 3 phenotypes for each trait (Pre, Post and Delta [Post – Pre]). From the blood samples innate and adaptive responses (counts of: white blood cells (WBC), neutrophils (NE), lymphocytes (LY), monocytes (MO), eosinophils (EO) and basophils (BA)) were measured. In addition, feedlot average daily gain (ADG), health records (HR) and lung scores (LS; collected at harvest) were also measured. Traits ADG, HR and LS have all been significantly correlated with infection to BRD. In this investigation we aimed to find correlations between the immune response and ADG, HR and LS; finding an easily measurable trait which would be a good predictor of the efficacy of vaccination. The results showed a positive Delta for the innate immune response (EO, BA, NE), while the adaptive immune response had a negative Delta (LY). Overall, we discovered that the immune responses had moderately high heritabilities (lowest: Delta MO, 0.21; highest Pre LY: 0.5), with LY having the highest h2 throughout the study (h2=0.41). All significant genetic correlations were calculated using bivariate REML models. While LS did not significantly correlate with any of the immune phenotypes, both ADG (LY, -0.24) and HR (Pre EO, -0.67; Delta WBC, -0.5 and Delta LY, -0.67) did. Interestingly all the significant genetic correlations were negative, suggesting successful immunization of animals appears to be a function of a high level of LY pre-booster and a low negative (or positive) Delta, of WBC and LY, 21 days after the booster vaccination is administered. The increase in EO and BA may potentially link their role in decreasing LY. These results may enable farmers to quarantine, re-vaccinate and breed animals to lower the incidence of BRD post-vaccination.