Heat Stress in Cattle
Heat stress in cows happens when they can’t dissipate the heat they generate, leading to discomfort and lower milk yields. Unlike humans, cows can start feeling heat stress at temperatures above 20°C. You might notice that your cows breathe faster, graze less, drink more, and move slower in warm weather.
Providing shade and ample drinking water is the first line of defence against heat stress. You can also make strategic changes to their management and feeding routine. The podcast included here provides scientific explanations and in-depth strategies for managing heat stress.
Why do cows get hot so easily?
Heat stress occurs when cows have more heat than they can get rid of and leads to discomfort and lower milk production. All areas of New Zealand get hot enough to cause heat stress during summer.
We all have an ideal temperature range within which we feel comfortable and our immune system and organs function properly. The comfortable temperature range for a cow is 4-20°C, lower than for a human of 16-24°C.
That’s because cows generate enormous amounts of energy digesting food and producing milk. This is handy during winter but a challenge during summer, when cows absorb more heat from the environment and it’s harder for them to maintain an ideal body temperature.
One way cows get rid of excess heat is by evaporation through their breath and sweat.
To increase evaporation, they breathe faster and sweat more, although their ability to sweat is limited. When this isn’t enough, they eat less to reduce the production of heat in their rumen, so their milk yield declines.
High humidity, little cloud cover, and low air movement increase the risk of heat stress as evaporation is less effective, making it hard for the cow to lose heat by sweating and panting.