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Ag meteorologist warns of livestock heat stress dangers

Photo by Stephen Patton University of Kentucky horse drinking water.jpg
Fresh, clean water is vital during heat waves.
Excessive heat warnings in place across much of Central U.S. as well as Eastern Seaboard.

It’s already hot outside, but University of Kentucky agricultural meteorologist Matthew Dixon said it would get even hotter over the weekend, and livestock producers and horse owners need to do what they can to minimize animal stress.

Noting that much of Kentucky is under an excessive heat warning through the evening of July 21, Dixon said, “We expect highs to jump into the low to middle 90s each day. Some areas hitting the upper 90s cannot be ruled out. Combined with elevated humidity, peak heat indices will likely run between 100 and 110 degrees. This heat will push the livestock heat stress index into the 'Danger' to 'Emergency' categories during the afternoon and evening hours.”

Excessive heat warnings are in place across much of the Central U.S., from eastern Nebraska to Ohio, as well as for the Eastern Seaboard, according to the National Weather Service.

National Weather ServiceUS heat warning.jpg

The combination of heat and humidity can cause concerns for livestock.

“The livestock heat stress index helps us determine what level of concern farmers and pet owners need to have for their animals,” said Dixon, who works with the Agricultural Weather Center in the University of Kentucky College of Agriculture, Food & Environment. “That index helps producers know when heat stress could create a problem for their animals so they can be even more vigilant in making sure they have to the necessary resources to combat the stress.”

Many livestock producers are familiar with the steps they need to take to help animals endure these dangerous conditions.

“The most important thing producers can do is provide cool, clean water and shade,” University of Kentucky beef specialist Jeff Lehmkuhler said. “It’s also a good idea to avoid working or transporting animals during periods of danger or emergency heat stress.”

Horses have difficulty regulating their body temperature when temperatures exceed 90°F, and if humidity is high, the temperature doesn’t even have to reach 90°F to make life uncomfortable.

“Horse owners can reduce heat stress by scheduling activities during the cooler part of the day and making sure horses have plenty of water,” University of Kentucky equine extension specialist Bob Coleman said. “If you do transport horses during the cooler part of the day, give water before, during and after transportation to reduce the risk of dehydration.”

Coleman added that even non-working horses will double their water intake during hot weather, and owners should allow horses to drink often to help maintain water balance.

“If you let them drink often, it can relieve the horse’s urge to drink a lot of water after exercise, as they need to gradually drink after a workout,” he said. “Also remember, lactating mares have special water requirements, because they are using water for milk production as well as body temperature regulation.”

Hot weather also increases horses’ need for salt, because they lose the mineral during sweating.

For dairy cattle, it is important to keep buildings as open as possible to allow air to circulate. Fans can make a big difference, and sprinkler systems that periodically spray a cool mist on the animals are also beneficial, the University of Kentucky said.

Poultry are especially prone to heat stress. Mortality during extreme heat can be significant, and egg production and hatching rates can drop.

“Since the birds don’t have sweat glands to help get rid of excess body heat, they have to pant to cool down,” Jacquie Jacob, University of Kentucky poultry extension project manager, said. “It’s important to make sure chickens are in well-ventilated areas and they have access to clean, cool water at all times.”

Dixon said the good news is that relief is on the way.

“A strong cold front will push through the region Sunday night, July 21,” he said. “This will bring a much more comfortable air mass to Kentucky over the next workweek.”

The University of Kentucky Agricultural Weather Center provides statewide and county-specific weather information, alerts, livestock heat stress conditions and more.

Kansas State University beef veterinarian A.J. Tarpoff is also sounding the bells for livestock producers to take some extra measures to protect their herds during a stretch of days in which temperatures are expected to top 100°F across the state.

“Water, water and lots of water,” advised Tarpoff, who noted that the beef industry loses an estimated $369 million each year due to the effects of heat stress. “Whenever we have a heat stress event, that is the most essential nutrient for animals, times five. I say ‘times five’ because the question always comes up about how much water cattle need, and the answer is that they need five times the amount of water that they are taking up in dry matter.”

For a cow that is consuming 30 lb. of dry matter, that comes out to about 20 gal. per day. Multiply that by the number of cattle in an operation, and the need for water grows exponentially.

Tarpoff said cows try to cool themselves by panting heavily (evaporative cooling) and somewhat by sweating, although they are inefficient sweaters compared to humans. Cows accumulate a heat load during the day and rely on cooler nighttime temperatures for relief.

Producers can aid in cooling not only by providing more water but also by changing some of their management strategies during the hottest days.

For example, Tarpoff noted, producers should consider providing most of the cattle feed later in the day, as much as 70%. Doing so will help to reduce digestive heat, or the heat that accumulates when cattle eat.

“This time of year, we may be providing that ration at 6:00 or 6:30 in the evening so we can push back that digestive heat load into the cooler hours of the night,” Tarpoff said. “That can make a big impact on how much these animals deal with during the heat of the day.”

Producers should also try to avoid lower-quality straw hay or other foods that are fibrous, which create more heat in the animal’s rumen. Feedlot rations and lush green grass are better options for helping animals control digestive heat, Tarpoff said.

In feedlots or other confined settings, producers should provide plenty of water and shade (if available) and use sprinklers to cool pen floors. Tarpoff also recommended minimizing animal handling, because the more the animals have to move, the more heat they produce.

The Kansas Mesonet Network at Kansas State University maintains a Cattle Comfort Index that combines the effect of temperature, humidity, wind and solar radiation. Tarpoff said it’s an excellent online source for producers to monitor when making plans for heat and potential nighttime cooling.

The Cattle Comfort Index is available online at http://mesonet.k-state.edu/agriculture/animal.

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