Wednesday, July 8, 2009

Beef Cattle Can Suffer In Heat Warns Extension Specialist

By David Burton
University Extension

When outdoor temperatures get hot, humans can take some precautions by going indoors, finding air conditioning, locating some shade and perhaps removing clothing.

In contrast, beef cattle do not have as many cooling choices.

“Cattle might be stuck in a pasture with limited or no shade, no pond to cool off in and worst of all, they may still have their long, winter hair coat on. Three inches of hair can put cattle into a heat stress mode in a hurry,” said Eldon Cole, a livestock specialist with University of Missouri Extension.

With the heat index recently surpassing 100 degrees Fahrenheit as the “feels like” temperature, producers need to be sure they are providing water and cooling options for their cattle but they should also be watching for fescue problems.

Why do cattle hold on to their winter coats? One reason that is fairly obvious is genetics.

A classic example of marked contrast is to compare a purebred Brahman to a Scotch Highland animal. One coat is slick most of the time while the other is bred to withstand a cold, damp climate.

“Even within the breeds of cattle most often seen in this area, there can be vast differences in shedding rate. Nutrition and management can be involved, but a lot of blame is placed on toxins produced by fescue,” said Cole.

Research has shown that the “wild” endophyte fungus is found in 70 percent or more of the fescue pastures in Missouri. The fungus produces an ergot-like toxin, mostly ergovaline, that causes poor blood circulation and a tendency for the cattle to retain haircoats.

In fact, some animals even seem to grow more hair in the warm weather when they have consumed ergovaline from fescue.

“Imagine how uncomfortable you’d be wearing your winter coat with a 105 degree heat index,” said Cole.

Cattle that are darker haired also tend to suffer more when temperatures and humidity rises. Cattle that may have experienced respiratory problems earlier may pant and show serious heat sensitivity. During the late-June Midwestern heat outbreak, several hundred cattle in feedlots in Nebraska and Iowa died.

“There possibly were even cattle here in southwest Missouri that died during that period if they were not given shade and water,” said Cole.

If they didn’t die, they likely gained less during that period and pregnant females may have lost pregnancies. Bull fertility can also be reduced.

“It is vital for cattle owners to provide an abundance of shade, at least 25 to 30 square feet per adult animal. Cattle crowded under a shade may even suffer more if air movement is restricted,” said Cole.

For more information, contact any of the MU Extension livestock specialists in southwest Missouri: Eldon Cole in Mt. Vernon, (417) 466-3102; Gary Naylor in Dallas County, (417) 345-7551; and Dona Funk in Cedar County, (417) 276-3313.

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