[MCN] Burn fossil fuels, kill cows

[Lance Olsen]

BMC Veterinary Research (2015) 11:291 DOI 10.1186/s12917-015-0607-2

Heat stress related dairy cow mortality during 
heat waves and control periods in rural Southern 
Ontario from 2010-2012
Katherine E. Bishop-Williams et al

Abstract
Background: Heat 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.

Results: For 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 = ¾ 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.

Conclusions: Southern 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.
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"Localized ecological systems are known to shift 
abruptly and irreversibly from one state to 
another when they are forced across critical 
thresholds. Here we review evidence that the 
global ecosystem as a whole can react in the same 
way and is approaching a planetary-scale critical 
transition as a result of human influence."

Barnovsky et al. Approaching a state shift in 
Earth's biosphere. Nature Volume 486, 07 June 2012
doi:10.1038/nature11018
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"We are living on the surface of this planet Š 
and with its climate and atmosphere. It has 
always been the task of mankind to find the right 
answer to the problem these conditions set us, 
and even today we cannot think that we have found 
a sufficient answer." p. 131

Quoted from The Individual Psychology of Alfred 
Adler, by Heinz L. and Rowena R. Ansbacher. 
1956. Basic Books

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