Dairy Farming
SUMMER HEAT STRESS IN COWS – BETTER MILK QUALITY WITH ANCO FIT
S
ummer heat stress in cows is known to reduce milk yields and milk quality, reducing the profitability of dairy farms, which is why it is important to find ways to effectively manage it on farms. Lactating dairy cows prefer ambient temperatures of between 5 and 25 °C, the “thermoneutral” zone. At ambient temperatures above 26°C, the cow reaches a point where she can no longer
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cool herself adequately and enters heat stress. Where as the upper critical limit of the thermoneutral zone for dairy cattle is between 25 °C and 26 °C, the temperaturehumidity index (THI) is below 72. Higher producing cows, and thus multiparous cows, are more sensitive to the effects of heat stress compared to lower producing or primiparous cows. As milk yield increases from 35 to 45 kg/d, the heat stress threshold
is decreased by 5°C. Recent studies show that modern cows become heat-stressed starting at an average THI of 68 with the levels of stress increasing with increasing THI values. Higher-producing cows exhibit more signs of heat stress than lower-producing cows because higher-producing cows generate more heat as they eat more feed for higher production. They must get rid of the extra heat generated
July-August 2020
