Heat stress requires extra animal care

Prevent heat stress by providing adequate water for outdoor dwellers and air movement for indoor dwellers

Dairy cattle and pigs breathe harder, beef cattle lie around and eat less, and all of them drink lots of water when temperatures rise above 25 C.

Those physical responses aren’t surprising but the potential for heat stress in livestock should be monitored, according to veterinarians.

Cooler nights are the saving grace for most western Canadian livestock, a benefit not always available to those in Eastern Canada where humidity can keep temperatures high all day and all night.

Even so, temperatures in the West, which have reached higher than 30 C for prolonged stretches in some regions, have production-limiting potential so adequate water for outdoor dwellers and air movement for indoor dwellers are key.

“We definitely have summertime temperatures that are above the mid-20s and that tends to be when animals typically experience heat stress,” said Dr. Betty-Jo Bradley, an Alberta veterinarian who specializes in dairy cattle.

“It depends a little bit on humidity levels, at what temperature they start to experience it, but yes, it is a thing at least for a few months.”

Heat-stressed animals are uncomfortable and produce less milk, so cooling strategies are wise for both animal welfare and economic reasons, she said.

“When animals are heat stressed, they eat less. Their rumen actually produces heat when they’re digesting feed. So when they’re not eating as much feed, it decreases their fibre intake, which can decrease their butterfat. But the biggest impact overall is a decrease in production.”

Bradley said most dairy barns are well ventilated and many producers also use tunnel ventilation or fans to create air movement to aid cooling.

As for water, Bradley said the average lactating dairy cow requires 120 to 150 litres per day but that can double in severely hot conditions.

“The issue tends to be access,” said Bradley. At least four linear inches per cow of access to drinkers are needed, especially considering cows’ tendencies to do things as a group.

Central Alberta dairy producer Heini Hehli said cows become lazy on 30 C days but heat stress is rare in his experience.

“Cows in our climate do not really suffer because of the cool nights,” he said.

His barn, like many others, is wide open at each end and large fans encourage air movement when needed. The shade also offers protection from extreme heat.

“Air movement is what we need,” he said. “We do look after them.”

Feedlot cattle don’t have the benefit of either fans or shade in most western Canadian situations.

However, Leighton Kolk, who operates KFL Feeders near Iron Springs, Alta., said heat stress does not seem to be an issue. Once again, cool nights provide relief for cattle.

The feedlot sometimes sprays water over the cattle in the pens, although heat isn’t the prime reason.

“The water we put on is probably 60 percent motivated by dust control,” said Kolk.

“But generally dust is associated with really hot temperatures because cattle, when it’s hot, they just lie around and don’t do anything during the day and then it cools down at night and that’s when they stir up and get moving, and stir up dust clouds.”

A sprinkling of water doesn’t do much to cool the animals, he said.

“But the pen has a little bit more moisture and dust control, which helps cool the pen a little bit for the rest of the day. In an outdoor situation, there’s not a lot you can do for heat control. We adjust our ration so that the cattle eat a little less forage (that) causes heat production in the rumen.”

Dr. Roy Lewis, a large animal veterinarian, said in a recent Cattlemen column that cow-calf pairs need about 90 litres of water per day when it’s hot, so dugout or water source capacity has to be calculated accordingly.

As for hog operations, Alberta Pork chair Dan Majeau said that because most production is indoors, barns are designed with good ventilation.

“Basically, a system will cool within one degree of the outside temperature.… It’s warm but not sweltering and systems like misters can be used as well.

“There’s a number of barns that are equipped with the mister system or it can be temporarily done too, but for the most part the ventilation is adequate.”

Majeau said a transport quality assurance program guides the industry when shipping in hot weather. Shipping at cooler times of day and reduced load density are among the measures to limit heat stress and animal losses.

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