Temperature and humidity affects dairy cows' willingness to be on pasture

• When cattle are kept outside during the winter in Sweden the management is regulated trough the animal protection law regarding provision of shelter. This is, however, not the case during the summer grazing period. The effect of temperature humidity index (THI, mean 60.5, range 32.5 – 77.4) on dairy cows willingness to be on pasture was examined. Four years of information from Kungsängens Research farm regarding milk production and time for passing a gate between the barn and pasture of dairy cows milked in an AMS were studied. In total the production (average 26.8 kg milk/day) and behaviour data from 143 Swedish Red cows spread over lactation 1 to 6 was analysed for time spend on pasture and daily milk production in relation to THI. The cows could move freely between the barn and pasture, which were situated around the barn (between 50-260 m from the barn to the entrance of the pasture) and they were fed concentrate according to milk production in the barn. Weather data (temperature and humidity) was collected from a weather station 3 km from the barn. On average the cows spent 7:48 hr on pasture during 24 hrs. The duration spent outdoors was affected by the daily maximum THI and the time decreased with 2:25 min when THI increased with 1 (P<0.001). An increase in maximum temperature on its own did also negatively affect the duration the cows spent on pasture and for each 1 degree increase in maximum temperature the cows spent 2:31 min less on pasture per day (P<0.001). A high daily mean THI did not affect the milk production on the same day, but it negatively affected the milk production two days after with 0.026 kg when mean THI increased with 1 (P<0.01). These results show that even under Swedish conditions heat stress might negatively affect dairy cow and an increase in temperature and humidity might be associated to a decrease in time spent on pastures and a lower milk production. However more refined studies are needed in order to answer this question more thoroughly

Ämnesord

LANTBRUKSVETENSKAPER  -- Veterinärmedicin (hsv//swe)

AGRICULTURAL SCIENCES  -- Veterinary Science (hsv//eng)

LANTBRUKSVETENSKAPER  -- Husdjursvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Animal and Dairy Sience (hsv//eng)

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