|Chitko Mckown, Carol|
|Kachman, Stephen -|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 30, 2013
Publication Date: August 1, 2013
Citation: Leach, R.J., Chitko-McKown, C.G., Bennett, G.L., Jones, S.A., Kachman, S.D., Keele, J.W., Leymaster, K.A., Thallman, R.M., Kuehn, L.A. 2013. The change in differing leukocyte populations during vaccination to bovine respiratory disease and their correlations with lung scores, health records, and average daily gain. Journal of Animal Science. 91(8):3564-3573. Interpretive Summary: Bovine Respiratory Disease (BRD) is the most economically important disease in U.S. feedlots. Infection can result in morbidity, mortality, and reduced average daily gain. The long term goal is to lower the incidence of BRD using trusted genetic tools and methodology. In this investigation, immune response was determined after vaccinating a herd of 2,182 cattle. Vaccination started a significant immune response that varied greatly between animals. Further, genetic associations were estimated between different forms of immune responses and average daily gain or health records. Resistance to BRD following vaccination increases with higher levels of lymphocytes and white blood cells. These results may enable producers to predict if re-vaccination, quarantine, and (or) breeding of animals is required to lower the incidence of BRD post-vaccination. Further, use of the immune parameters measured can aid genetic, and potentially genomic, selection of animals resulting in more resistance to BRD.
Technical Abstract: Bovine Respiratory Disease (BRD) is the most economically important disease in U.S. feedlots. Infection can result in morbidity, mortality, and reduced average daily gain. Cheap and reliable genetic methods of prediction and (or) protection from BRD would be highly advantageous to the industry. The immune response may correlate with BRD incidence. Cattle (n = 2182) were vaccinated against common viral and bacterial pathogens of BRD. Two blood samples were collected, during booster vaccination and 21 d 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) and binary traits of health records (HR; 0 = healthy, 1 = ill), and lung scores (LS; collected at harvest; 0 = no lesions, 1 = lesions) were also recorded. Traits ADG, HR, and LS have all been significantly correlated with infection to BRD. In this investigation, correlations between the immune response and ADG, HR, and LS were examined to find an easily measurable trait which would be a good predictor of BRD resistance following vaccination. The results showed an average positive delta for the innate immune response (EO, BA, NE), while the adaptive immune response had an average negative delta (LY). Overall, the immune responses had moderately high heritabilities (lowest: delta MO, 0.21 ± 0.05); highest pre LY: 0.5 ± 0.05), with LY having the highest h**2 throughout the study (h**2 = 0.41). All genetic correlations were calculated using bivariate REML models. While LS did not significantly correlate with any of the immune phenotypes, both ADG (post LY, -0.24 ± 0.12) and HR (pre EO, -0.67 ± 0.29; delta WBC, -0.5 ± 0.24, and delta LY, -0.67 ± 0.21) did. All the significant genetic correlations with HR were negative; resistance to BRD appears to be a function of higher delta LY and WBC. The increase in EO may potentially link its role in decreasing LY. These results may enable producers to predict if re-vaccination, quarantine, and breeding of animals is required to lower the incidence of BRD post-vaccination. In addition, the use of the immunological phenotypes may be used to aid genomic selection indices to select animals with higher rates of protection following BRD vaccination.