Analysis of health and survival in a population of Ontario Holstein heifer calves.
McCorquodale, C.E., Sewalem, A., Miglior, F., Kelton, D.F., Robinson, A., Koeck, A., and Leslie, K.E. (2013). "Analysis of health and survival in a population of Ontario Holstein heifer calves.", Journal of Dairy Science (JDS), 96(3), pp. 1880-1885. doi : 10.3168/jds.2012-5735 Access to full text
The objective of the present study was to investigate health and survival in heifer calves, from 16 farms in southwestern Ontario. Research technicians visited the farms on a weekly schedule for 16 mo, starting in January 2008, and collected blood samples and various measurements to determine the overall health status of the calves. Data of 1,588 Holstein heifer calves from birth until 90 to 120 d of age were analyzed. Initially, a survival analysis was carried out to determine which factors surrounding birth increased a calf's risk of mortality. The factors examined were type of birth, calving ease, season of birth, serum total protein, weight during first week of life, treatment status during first week of life, total number of treatments, and bovine respiratory disease status. In general, calves born in fall (October–December), low serum total protein, low weight, and calves treated for illness during the first week of life, increasing number of treatments, and being treated for bovine respiratory disease all increased a calf's risk of mortality. Genetic parameters for requiring treatment for illness, survival, bovine respiratory disease, other diseases, height, and weight were estimated. Heritabilities for treatment, survival, and diseases were low, ranging from 0.04 to 0.07, and were not significant. Moderate and significant heritabilities were found for height (0.33 to 0.45) and weight (0.24 to 0.44). Treatment and survival to 90 to 120 d of age were favorably correlated, indicating that calves requiring less treatment have a higher survival rate and vice versa. Further, body weight was found to have a tendency of favorable genetic correlation (−0.22 to −0.53) with treatment for diseases, indicating that calves with higher body weight in their first month of life were genetically more resistant to diseases than those with average body weight. Overall, our results show the potential of using data on calfhood disease and survival in future dairy cattle breeding programs. Further investigation and improved data collection are required to determine the full impact of genetics on health and survival in dairy heifer calves.
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