Take steps to mitigate heat stress

10 Aug 2020

With temperatures rising above 25°C, producers should be mitigating the negative effects of heat stress on their herds.

“Cattle are fairly comfortable when the ambient temperature is between 15°C and 25°C during the summer months, but if the thermometer rises significantly, production performance will start to suffer,” warns Azelis Animal Nutrition’s Jacob Lakin.

Body heat

“This is because cows will start to divert energy away from milk production and towards keeping cool.

“You’ll notice if a cow is struggling during a summer heatwave because she will start to salivate heavily and pant. These are both mechanisms to increase the amount of body heat lost via evaporation.”

Rumen function

Mr Lakin adds that rumination may slow too, which will depress feed intake. “Rumen function and the process of fermentation generates a lot of heat, so limiting rumination is an innate response to heat stress. As a result, dry matter intakes will fall.”

He says that acidosis is also an associated risk. “This is because the cow will have a preference for less fibrous feed materials and concentrates, to decrease rumination.

“Consequently, rumen buffering capacity falls and acidosis can be triggered.”

Practical mitigation

Mr Lakin explains that two of the most effective and practical mitigation measures during a hot spell are to make sure both housed and grazing cattle have access to a constant supply of fresh water.

Producers can also introduce a rumen buffer, such as sodium bicarbonate, to the available ration.

Sodium bicarbonate is a simple, cost effective rumen buffer that helps to counter the loss of carbon dioxide in the lungs and bicarbonate in the blood caused by this increased breathing, and also the loss of sodium, potassium and bicarbonate due to increased sweating.

Provide shade

The recommendation is to add sodium bicarbonate to the ration up at a rate of between 250g and 300g per head per day for lactating cows. This costs between 8p and 9p per head per day.

“Cows can easily drink 100 litres of water a day during warm periods of weather, so make sure they have good access to it – ideally in the shade,” adds Mr Lakin.

Feeding routine

“Recognise too that the cow may alter her feeding routine, preferring to eat during the evening or at night when temperatures are cooler. Either way, ensuring that the ration is well buffered will help to boost intakes and offset any drop off in performance.”