Stress endangers bovine health

Very cold temperatures are hard on livestock and their offspring

By LEE JUILLERAT
H&N Regional Editor

January 8, 2009

Cattle near Klamath Falls enjoy the warmer temperatures this week, which make for more stress-free days.

When it’s cold, windy and wet outside, humans aren’t the only ones who suffer.

Livestock, including cattle and sheep, also feel the effects.

Chanda Engel, who deals with livestock and forage for the Oregon State University-Klamath Basin Research and Extension Center, says climatic conditions create stress that can affect not only the health of the livestock, but also their potential spring calves or lambs. Those stresses are especially noticeable in the Klamath Basin because of the typically wide swing in temperatures and conditions.

“That’s a lot harder on animals,” Engel said. Basin winter temperatures can vary 30 or more degrees, which prevents animals from adapting to routinely cold temperatures seen in areas like the Midwest.

Factors that create stress during the winter include cold, wind, snow, rain and mud. Individually and collectively, the factors increase an animal’s demand for energy. Much like humans, livestock increases metabolic heat production to stay warm, such as by shivering, Engel said. And, again like humans, cattle and sheep are affected by wind-chill factors, not simply ambient temperatures.

Wet weather, from rain, snow or dampness caused by mud, also affects cold weather stress. During wet times, damp hair and matting results in the loss of insulation, which effectively reduces body temperature. Based on studies, spring calving cows, especially heifers, in poor body condition are at risk for calving problems. As a result, calves may be lighter, weaker and more susceptible to other problems.

Engel said there are ways to reduce those negative impacts, including providing windbreaks and shelters to reduce wind, moisture and mud. She recommended feeding locations and buildings be on south-facing slopes for added protection from wind and areas where moisture conditions are lower. The use of bedding during severe cold or wet weather allows livestock to lie down without directly contacting frozen or wet ground.

“Muddy conditions can cause animals to reduce their feed intake,” she said. “That’s when bedding would be very helpful.”

She also said feed should be increased to accommodate for the extra energy spent staying warm. For example, Engel suggested a feed ration for a 1,250-pound cow during cold winter periods increase from about 35 pounds of hay a day to 38 to 43 pounds. And, she added, if feeding is done once a day, feeding the evening is more effective. Dry cattle stress less

Livestock health during cold winter months is influenced by an animal’s lower critical temperature, which is the effective ambient temperature below which an animal must increase its rate of heat production to maintain a constant body temperature.

Based on data from the West Beef Resource Committee, lower critical temperatures are defined as the temperature below which the rate of performance begins to decline as the temperature becomes colder. Temperatures below the thermoneutral zone constitute cold stress. Cold stress may change from 32 degrees F for cattle with a dry winter coat to 60 degrees F if the coat is wet.

“A good rule of thumb is that for every degree below the critical temperature, the cow’s energy requirement increases by 1 percent,” said Chanda Engel, a livestock and forage extension agent with the Klamath Basin Research and Extension Center.

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