Tackling heat stress in dairy cattle and best ways to minimise the problem

Heat stress occurs when a cow’s heat load is greater than its capacity to lose heat.

Dr Laura Tennant, ruminant technical specialist with Trouw Nutrition, says: “Cows suffering from heat stress will produce less milk with poorer milk composition with declines in both fat and protein content.

“Heat stress can affect rumen function. Chronic heat stress and reduced rumination can lead to a depressed immune system, triggering a decrease in resistance to bacteria and an increase in somatic cell counts”.

Forage

She advises trying to keep cows on good quality forage, explaining that more mature grass and other feeds with a high fibre content increase the heat generated by rumen fermentation, increasing the internal heat load at a time when the cow is trying to cool down.

She recommends offering buffer and other supplementary feeds in the evening when it is cooler to promote better intakes.

When cows are at grass, she recommends using paddocks with shade during periods of heat stress and reducing the walking distance and speed between the grazing and parlour.

Shade

“Consider changing the rotation, so cows are in unshaded paddocks in the evening,” she says.

“Allow cows access back to shaded yards and reduce the time spent in unshaded yards.”

She also advises taking steps to minimize any handling stress and to isolate cows most severely affected by heat stress and providing greater shade and cooling.