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The effect of heat stress on the behaviour of dairy cows at the drinker

University of British Columbia

Heat-stressed dairy cows on pasture will compete for resources that aid cooling, but it is not known how heat stress affects the competition for water by indoor housed cows, or if competition for water can be recorded automatically with an electronic drinking system. The objectives of my thesis were to 1) validate an electronic drinking system to detect social competition between dairy cows at the drinker by identifying the interval between one cow leaving the drinker and another cow taking her place, and 2) evaluate how heat stress affects the behaviour of indoor-housed cows at the drinker, both at group and cow level. For the first objective, 20 cows were monitored for 4-d by video recording and an electronic drinking system. Replacements (defined as when physical contact initiated by one cow causes the other to remove her head from the drinker with the initiator subsequently placing her head in the same drinker), identified by video, were paired with the interval between drinking events of the 2 cows at the electronic drinker, to identify the interval that best predicted replacements. The optimal interval to identify replacements at the drinker was ≤ 29 s. For the second objective, 69 cows were observed over 59 d. The electronic drinking system recorded time spent at the drinker, frequency of visits, water intake, and competitive replacements. The number of replacements a cow was involved in was used to determine her level of competitive success at the drinker (low, medium, high). The temperature-humidity index (THI) was recorded by the local weather station. With increasing THI, cows drank more water, spent more time at the drinker, made more visits, and engaged in more replacements at the drinker. We also found that cows with low competitive success at the drinker shifted their drinking behaviour to avoid the drinker at the hottest and most competitive time of day. These results indicate that competition between dairy cows at the drinker can be accurately measured with an electronic drinking system, and that drinking behaviour can be used to indicate when cows feel hot.

Text

2019-12-03

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/72534

Applied Animal Biology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/