LEWIS, Iowa ― When temperatures plunge into the single digits and the winds howl, people pile on the outerwear and look for warm food and beverages to help ease the chill. Chris Clark, Iowa State University Extension and Outreach beef program specialist, said it’s important to remember that although Iowa cattle typically can tolerate winter conditions surprisingly well, colder temperatures can mean higher nutrition needs for cow herds.
“Iowa cattle have thick skin, grow a thick winter coat and will be insulated by any fat cover they may carry. They also have the rumen, a large fermentation vat in the abdomen that produces heat during the digestion process,” Clark said. “Even so, during times of extreme low temperatures, cows can become cold enough to have a big impact on health and production.”
For each degree of cold stress below the animal’s lower critical temperature (LCT), the animal requires about 0.7 percent more energy just to maintain its body weight. The LCT is around 20 degrees for cattle with a heavy winter hair coat, but can increase to 50-60 degrees if the animals get wet.
“Don’t forget that wind, rain, snow and other weather conditions have an impact on the animals as well,” Clark said. “Wet animals, strong winds and deep snow all add to the cold stress, so make sure to provide adequate nutrition to meet the high energy demands of fetal growth and winter weather on your cows.”
As a general rule of thumb, each additional 10 miles per hour of wind speed to which cattle are exposed has the same effect as dropping the temperature 10 degrees.
“Keep an eye on thin cows because they lack the insulation of fat cover and will be more susceptible to cold stress and hypothermia,” Clark said. “A simple windbreak or a roof to keep them dry can make a big impact on animal comfort as well as on health and productivity.”
Following the drought of 2012, some cows may have come into the winter thinner than usual, so it might be wise to sort off thin cows to a separate area, he said. This way you can provide them with a higher quality ration while eliminating competition from other cows. Also, because last year’s drought may have taken a toll on quantity and quality of available forages, some producers are feeding CRP hay, corn stalks and other lower quality forages.
“If you are using lower quality forages, it’s important to supplement those forages appropriately to meet animal requirements,” Clark said. “Nutrient requirements go up throughout third trimester and early lactation, so cows that are thin right now will need a high plane of nutrition to keep up with fetal growth, milk production and Iowa winter weather.”