The hot summer months can present some challenges for cattle herds.
Jim Humphrey raises cattle and works as a University of Missouri Extension livestock specialist based in Andrew County. He says heat can affect cattle performance.
“Performance is probably the biggest thing,” he says. “Especially with stocker calves, we get really hot like that, we get lower average daily gains.”
Humphrey says stocker calves and cows graze less during hot days.
“They don’t want to be out grazing,” he says. “If they find a good spot in the shade, they stay there.”
Extreme heat can also cause aborted pregnancies, and it can affect fertility in bulls long-term, he says.
Iowa State University Extension veterinarian Grant Dewell says reproductive issues are the top concern for cow-calf producers in the summer heat.
“Reproduction is the biggest one that we generally see,” he says.
Dewell says embryos sometimes don’t implant if conditions are too hot, leading to open cows. In addition to causing fertility issues down the road in bulls, heat can keep them from venturing around to breed cattle.
“If it’s hot enough, bulls don’t get too active,” he says.
Higher body temperatures can impact pregnancy rates.
“One of the reasons they come up open, they just had a little higher body temperature,” Humphrey says.
Heat concerns can start at lower temperatures, Humphrey says.
“Once we typically get above 70 degrees, beef animals, that’s above their thermoneutral zone,” he says. “They like to be about 70 degrees or less.”
This can vary a few degrees by breed, Humphrey says. Then the extreme temperatures ramp up the issues.
“Once we start getting above 90 or 100 on the heat index, we really see some heat stress effects,” he says.
Dewell says in temperatures from the 70s to 90, their bodies can generally regulate well.
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“They’re having to actively cool these bodies off, but they’re doing OK,” he says.
In hotter temperatures, cattle often need extra help like shade and additional water.
“When the forecast is 95 degrees, we’re going to have some heat stress for cattle,” Dewell says.
To care for cattle and reduce the impacts of heat, Humphrey says water is the key factor.
“We want to make sure the animals have plenty of fresh, available water,” he says. “The No. 1 thing we can do is provide cool, clean water for them.”
Making sure cattle have shade access also helps, whether it is trees or structures and other manufactured shade.
“Protection from the sun is a good thing,” Humphrey says.
Abundant shade options avoid having animals too closely packed together, which could lead to injuries or younger calves getting stepped on.
Dewell says producers can manufacture shade as needed with portable umbrella structures. Some operations also have livestock buildings to provide shade.
“Shade is a big deal,” he says.
Dewell says death loss from heat is mostly a concern in feedlot situations, but shade, abundant water and even water misting systems can help keep feedlot cattle cool.
Dewell says while producers generally keep cattle out of water to protect the water supply, they could let them in ponds for a little while to let them cool off.
Also, he says producers should be mindful that fescue toxicity issues are most pronounced during the heat of summer, so they should be watching cattle’s diets. Taking care of fly issues can also minimize other stresses during the hot months.
Humphrey says if producers are feeding supplemental feed or having to feed hay due to drought conditions, feeding in the evening is a good idea.
“When that digestion starts really going, it’s in the evening and the night when there’s less stress,” he says.
If producers are doing supplemental feeding in hot conditions, Humphrey says it is good to reduce the high-starch grains and feed more forages, such as hay, if needed.
As for a long-term way to manage heat stress, Humphrey says producers can pay attention to how well cows shed their winter coat.
“Some of these animals that keep their shaggy coat on still, they probably have a little higher body temperature,” he says. “Something you can be selecting for, these animals that shed their hair earlier, and more completely.”
