June 9, 2004 | By: Ellen Brightwell

To reduce livestock heat stress, it is important to provide plenty of food, water and shade and maintain good animal health. Producers may need to use other techniques to lessen heat stress for specific species.

“The key to managing cows during the summer is to get them to eat as much as possible,” said Donna Amaral-Phillips, Extension dairy nutritionist with the University of Kentucky College of Agriculture.

“Dairy cows become stressed and eat less feed when the temperature and humidity rise,” she explained. “As feed intake decreases so does milk production.

“High-producing cows are the most susceptible to heat stress. Bred heifers and dry cows also suffer from heat stress as indicated by smaller calf birth weights and lower production in the upcoming lactation. Milking cows and cows and heifers within three weeks of calving are the most important groups to keep cool.”

Amaral-Phillips suggested some practices to encourage heat-stressed dairy cattle to eat more. 

Since cows consume about 70 percent of their feed after midnight and during early morning, provide plenty of feed at night when animals want to eat. Cows produce a tremendous amount of heat when digesting their feed so encourage them to eat early in the day so this heat does not peak at the hottest time of the day. The maximum heat load is four hours after feeding. 

Feed smaller, more frequent meals during the day to decrease heating of feed in bunks. Clean feed bunks daily to encourage intake.

“When feed intake declines, it may be necessary to rebalance rations to give cows needed nutrients,” Amaral-Phillips said. “Summer rations should contain a little bit more sodium and potassium to replace minerals lost when cows sweat and pant.”

Grazing endophyte-infected tall fescue exacerbates heat stress in cattle because the toxins cause an elevated body temperature, according to Darrh Bullock, Extension specialist in beef breeding and genetics. Decreased milk production, lower rate of weight gain, and reduced reproductive performance are the most important economic responses to this fescue toxicity.

Bullock recommended diluting fescue with legumes, especially clovers. Research continually shows higher rates of gain and conception rates when legumes are a major part of fescue pastures. Another alternative is to use another grazing option such as warm season grasses.

Horses have difficulty maintaining their body temperatures when asked to work in hot, humid conditions, according to Bob Coleman, Extension horse specialist.

To determine whether a horse should be ridden under these conditions, Coleman recommended using the comfort index, which is calculated by adding the relative humidity to the temperature.

“There should be few problems when the comfort index is below 130,” he said. “But be cautious if it is between 130 and 150 because the horse can’t lose heat as effectively and may not be able to maintain its body temperature. Do not ride if the comfort index is above 180 degrees.

“Call a veterinarian for a heat-stressed horse, because it may be necessary to use intravenous fluids to replace the significant amount of water lost during sweating. 
Meanwhile, move the horse into shade, fan it and spray the body with water to lower its body temperature. It is very important to give the horse small sips of water frequently to aid re-hydration. “

Providing ample water helps animals regulate their body temperatures to relieve heat stress. Be sure the water is cool, clean and easily accessible. When temperatures are especially hot, livestock may not leave the comfort of shade to find water so locate waterers to limit animal travel.

“Avoid using a pond that allows cattle wading access because the water can become warm and dirty, resulting in decreased consumption,” Bullock said. “Instead, fence ponds and offer water through a tank.”

“A good way to lessen heat stress is to provide plenty of shade for livestock,” said Monty Chappell, Extension sheep specialist. “It is especially important to provide shade in higher elevation areas and rolling terrains to encourage air movement. Periodically move portable shades to prevent trampling and muddy areas.”

Since shade alone may not provide adequate heat stress relief for dairy cattle, using fans and sprinkler systems provides additional cooling, according to George Heersche, Extension dairy specialist.

“Wetting the cow with water by sprinkling, not misting, and using fans to evaporate the water generates extra cooling,” he said. “Research shows an 11-percent increase in milk yield for cows cooled with fans and sprinklers compared to shading alone. Putting sprinklers and fans next to the feed bunk will cool the area and encourage greater feed intake.”

Combining water and fans also lessens the heat stress in swine confinement facilities, according to Richard Coffey, Extension swine specialist.

“Be sure the cooling or water-mister system is properly operating,” he said. “For an evaporative-cooling system, check the operation and functioning of the water line, sump pump and evaporative pads. On spray-type systems, be sure spray nozzles, drippers and misters are not plugged up and are releasing the proper amount of water at the correct intervals.”

Coffey said it is important to also check for proper operation of animal waterers.

“Animals will die from dehydration much quicker than they will starve to death,” he said. “Be sure waterers are providing all the clean, fresh water animals want to drink. Remember to also inspect the flow rates on nipple waterers.”

A properly working ventilation system moves enough air through the swine facility to remove heat and reduce humidity. For the most efficient use, check the operation of controllers and fans. Adjust inlets to ensure good air distribution and mixing.

“Healthy animals can better withstand heat stress,” Chappell said. “Producers need to pay attention to livestock health to reduce stresses from internal and external parasites and other disease challenges.

“Handle all livestock only for essential procedures and perform work before sunrise, the coolest part of the day,” he said. “Be sure you have adequate labor available for quick and efficient work.”

Sources: Donna Amaral-Phillips 859-257-7542

Darrh Bullock 859-257-7514

Bob Coleman 859-257-9451

George Heersche 859-257-5987

Monty Chappell 859-257-2716

Richard Coffey 257-365-7541 Ext. 244


Writer: Ellen Brightwell  859-257-4736 ext. 257