Cattle producers who provide gestating heifers with windbreaks or shelters against the cold may reduce the incidence of calving difficulties. Prolonged low temperatures and freezing wind-chills during the winter months can mean larger calves born during February and March, says David Colburn, researcher at the University of Nebraska West Central Research Center in North Platte.

Mr. Colburn measured air temperatures, wind chills, calf weights and calving difficulty during three consecutive calving seasons. He found that when average temperatures increased 11 degrees from 1993 to 1995 the average calf weight dropped 11 pounds, from 81 to 70 pounds. Calving difficulty decreased 22 percent.

"When a pregnant animal is exposed to cold temperatures, blood is concentrated internally to maintain its core body temperature," says Mr. Colburn. "During prolonged periods of cold weather, the fetus may receive more nutrition because more blood flows to the uterus."

Nutrition, sire and dam genetics, calf gender and climatic conditions all affect calf size at birth. Providing shelter for high-risk cattle during extreme cold may be one more little way to improve your herds calving percentages and increase profits.