Heat stress related dairy cow mortality during heat waves and control periods in rural Southern Ontario from 2010–2012

BMC Veterinary Research

Research Article

David L. Pearl¹  Katherine E. Bishop-Williams¹  Olaf Berke²  David F. Kelton³  Karen Hand⁴ 

[1]Department of Population Medicine, Ontario Veterinary College, University of Guelph, 50 Stone Rd East, N1G 2 W1, Guelph, ON, Canada

[2]Department of Population Medicine, Ontario Veterinary College, University of Guelph, 50 Stone Rd East, N1G 2 W1, Guelph, ON, Canada

[3]Department of Mathematics and Statistics, University of Guelph, Univof Guelph, 50 Stone Rd East, N1G 2 W1, Guelph, ON, Canada

[4]Institute of Biometry, Epidemiology and Information Processing, University of Veterinary Medicine, Hanover, Germany

[5]Department of Population Medicine, Ontario Veterinary College, University of Guelph, 50 Stone Rd East, N1G 2 W1, Guelph, ON, Canada

[6]Strategic Solutions Group, 142 Hume Rd, Puslinch, ON, Canada

[7]Strategic Solutions Group, 142 Hume Rd, Puslinch, ON, Canada

关键词: Southern Ontario;    Heat stress;    Rural;    Dairy cow;    Mortality;   

DOI  :  10.1186/s12917-015-0607-2

 received in 2014-07-16, accepted in 2015-11-24,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundHeat stress is a physiological response to extreme environmental heat such as heat waves. Heat stress can result in mortality in dairy cows when extreme heat is both rapidly changing and has a long duration. As a result of climate change, heat waves, which are defined as 3 days of temperatures of 32 °C or above, are an increasingly frequent extreme weather phenomenon in Southern Ontario. Heat waves are increasing the risk for on-farm dairy cow mortality in Southern Ontario. Heat stress indices (HSIs) are generally based on temperature and humidity and provide a relative measure of discomfort which can be used to predict increased risk of on-farm dairy cow mortality. In what follows, the heat stress distribution was described over space and presented with maps. Similarly, on-farm mortality was described and mapped. The goal of this study was to demonstrate that heat waves and related HSI increases during 2010–2012 were associated with increased on-farm dairy cow mortality in Southern Ontario.Mortality records and farm locations for all farms registered in the CanWest Dairy Herd Improvement Program in Southern Ontario were retrieved for 3 heat waves and 6 three-day control periods from 2010 to 2012. A random sample of controls (2:1) was taken from the data set to create a risk-based hybrid design. On-farm heat stress was estimated using data from 37 weather stations and subsequently interpolated across Southern Ontario by geostatistical kriging. A Poisson regression model was applied to assess the on-farm mortality in relation to varying levels of the HSI.ResultsFor every one unit increase in HSI the on-farm mortality rate across Southern Ontario increases by 1.03 times (CI95% (IRR) = (1.025,1.035); p = ≤ 0.001). With a typical 8.6 unit increase in HSI from a control period to a heat wave, mortality rates are predicted to increase by 1.27 times.ConclusionsSouthern Ontario was affected by heat waves, as demonstrated by high levels of heat stress and increased on-farm mortality. Farmers should be aware of these risks, and informed of appropriate methods to mitigate such risks.

【 授权许可】

CC BY   
© Bishop-Williams et al. 2015