Cold stress becomes a risk for cattle when temperatures fall below the ‘thermo-neutral’ zone, where cattle are neither too hot nor too cold at the temperature range of 59-77 degrees F. Below this zone, maintenance energy requirement and the feed intake of beef cattle will be altered.
“However, the critical temperature for a cow will vary based on hair coat, moisture conditions, wind conditions and body condition score of the cow,” said Dr. Jeremy Powell, professor and veterinarian of the Department of Animal Science at the University of Arkansas. “When the hair coat is wet, the critical temperature is around 59 degrees F, although a dry winter hair coat creates a blanket of insulation between the cow’s body and the cold air so that her critical temperature for ‘cold stress’ will be closer to 30 degrees F. In periods of precipitation, wet hair will lose its insulating quality, and the cow will chill quicker.”
According to Powell, the usual response to cold stress includes muscles shivering, an increased heart rate, deeper breathing, and the metabolism rate is increased in all tissues. “This results in an increase in the cow’s requirements for energy intake.”
“Body condition and overall health of the herd play a big role in how well cattle can fair in cold weather,” said Andy McCorkill, regional livestock specialist in the Dallas County University of Missouri Extension office.
“Carrying a little extra flesh on your cattle going into winter isn’t necessarily a bad thing. Extra fat helps to insulate the body and also gives some stored energy reserve to help get through the worst of times. We like to see cows in the 5-7 range on the 1-9 body condition scoring system coming through winter into the calving season.”
Supplements are key to preventing cold stress. “A good rule of thumb is that for every one degree drop below the critical temperature, a cow’s energy requirement (TDN) increases 1 percent,” Powell said. “This means that when the temperature drops below her critical temperature, cattle need to be fed better. It’s ideal to use your higher quality hay at these critical times to provide for the increased needs.”
Newborn calves can be especially at risk for hypothermia in cold weather conditions. “Some spring calving herds begin having a few calves in late February and early March when weather conditions can still be extreme,” Powell said. “Studies have shown that adjusting the time of day you feed the pregnant cows will affect the time of day when she will have her calf. Evening feeding of the cows has proven to increase the percent of cows that give birth during daylight hours compared to night time hours lessening the risk of hypothermia since daylight hours are generally warmer.”
Good natural shelter such as timber and areas to keep out of the wind will help preventing any cold stress as well. “Access to dry bedding such as hay or straw will provide a buffer between cold wet ground and cattle as well as some extra insulation against the wind and cold temperatures,” McCorkill said.
Essential prevention includes vaccinating your herd against respiratory illnesses. “Develop a close working relationship with a good veterinarian and follow their advice on what vaccinations you need to be giving for your specific management system and location,” McCorkill said.
McCorkill added that proper nutrition will help overcome more obstacles than anything else. Remember to keep an eye on body condition and manage your feeding program around it. For further information, contact your veterinarian or livestock extension specialists.
