Why do some calves die and others thrive? An investigation of risk factors impacting male calf health in Ontario
This thesis is an investigation of the care of male calves on Canadian dairy farms, management factors on source dairy farms impacting mortality at veal farms, and clinical and metabolic factors impacting mortality after arrival at a veal facility. Finally, the diagnostic accuracy of bioluminescence in detecting contaminated colostrum feeding equipment was evaluated. A cross-sectional survey was used to evaluate the care of male calves on Canadian dairy farms. Most respondents always fed colostrum and always fed male and female calves the same. However, a minority of respondents always navel-dipped or vaccinated male calves. The care of male calves differed greatly depending on geographical region, herd size and familiarity with the Code of Practice for the Care and Handling of Dairy Cattle. There were several high-risk management practices impacting male calf health on veal farms identified through a cross-sectional study of source dairy farms sending male calves to two veal operations. The feeding method for colostrum, bedding used for male calves, veterinary involvement with calf health management, and the frequency of observation of the calving area were all associated with high mortality source dairy farms. Many calves entered the milk-fed veal facility with a health abnormality and most of the mortality occurred in the first three weeks following arrival. Several risk factors were identified through the use of both a cohort and case-control study design, such as abnormal navel, dehydration, and body weight at arrival were associated with early and late mortality in the growing period. A lower level of immunoglobulin G and cholesterol in the serum was also associated with greater odds of early mortality. Colostrum feeding equipment harbored a significant amount of bacterial contamination. Visual hygiene assessment was a poor indicator of bacterial count. The HygienaTM AquaSnap and MircoSnap luminometry swabs were shown to be reliable predictors of total bacterial and total coliform counts, respectively.