When summer arrives, we finally find ourselves taking those extra layers off and our bodies are enjoying warming up. But what about cows? They cannot take a layer off and often have a black coat...
Cows feel hot sooner than we do. Dairy cows need to maintain a constant body temperature of around 38-39°C. They are sensitive to any factor which influences the thermal exchange with the environment – like air temperature, wind, and humidity.
When an animal’s heat load is greater than its capacity to lose heat, it starts to suffer from heat stress. Heat stress often occurs in barn environments, but can also occur at grazing on hot days.
Signs of heat stress
The first sign of heat stress in dairy cows is clustering around the water trough or forming large groups as they try to get shade from each other’s bodies.
Cows with heat stress prefer to remain constantly standing, instead of lying down, so the air can move around their whole body and belly to help cool them down. Heat stress can therefore increase the risk of lameness as they stay on their feet!
Other, more obvious, signs of heat stress are panting (breathing faster than usual) and drooling (increased saliva production).
As most of the heat produced in dairy cows is due to rumen fermentation, the cow will reduce her dry matter intake by 10-30% to lessen the heat forming. Eating less also has the impact of reducing milk production.
Credit: DairyNZ
Managing heat stress
Have plenty of water sources/troughs available in paddocks, in laneways on the way to the shed, and in/near the yards. As we get into summer, cows will be drinking more. Their water intake can increase by 10-20% in hot weather! This increases even more if the cow is producing heaps of milk. However, cows are unlikely to walk far to drink if the water trough is a long distance away.
Cool cows down by providing shade, ventilation and cooling. The installation of large fans and sprinkler systems is often said to be a solution, but could be costly. Simple improvements in basic ventilation, such as a side opening for extra air flow in a shed, are less expensive but often remarkably effective to reduce heat stress.
Reduce any loss in milk production by addressing that dry matter intake decreases when temperatures increase. Maintain nutrient intake and increase energy density with greater amounts of concentrate and/or by-products. Consider more suitable forage options – low quality stemmy forages generate more heat when fermenting inside the rumen, while high quality forages are digested faster and result in less heat being produced. Feeding more concentrates, and using higher quality forage should help the cow maintain her energy requirements for good milk production even though she eats less dry matter.
Change feeding times. Cows tend to eat less overall during the day compared to overnight, but they eat more often and in smaller quantities. Feeding 60% of the ration between 8.00pm and 8.00am will increase feed consumption.
