While colder temperatures mean livestock producers need to be aware of increased livestock energy requirements, fallout from the summer drought might also play a role this winter, an Ohio State University Extension educator says.

Cold temperatures, cold rains and muddy conditions can significantly increase the energy required by livestock metabolism to provide enough heat for animals to maintain body temperature. But animals that have less body condition and fat as a result of grazing on drought-stressed pastures might need to have that additional supplement sooner to be able to produce the energy needed to weather the cold period, said Rory Lewandowski, OSU Extension agriculture and natural resources educator.

Animals in good body condition can call on fat reserves, but if they are in colder temperatures for longer periods, they need the increased energy content in rations to help them alleviate cold stress, Lewandowski said.

“Every year, going into the winter means that producers have to take into account weather conditions,” he said. “But in a drought year like this, we have to look at what kind of body conditions livestock has coming into the weather.

“If the herd is pasture-based, those animals may be coming in to winter in thinner body condition because our earlier drought conditions caused pastures to dry up and didn’t offer as much forage for livestock. Producers have to evaluate their herds’ body conditions and whether those animals can go through adverse weather.”

Animals have a thermoneutral zone - a temperature range in which the animal is most comfortable, not under any temperature stress and that is considered optimum for body maintenance, health and animal performance. But when livestock experience cold stress below the lower boundary of that zone, they reach lower critical temperature (LCT) and the animal’s metabolism must increase in order for it to keep warm, Lewandowski said.

“That means the animal must increase its energy intake to maintain body temperature and basic body maintenance functions,” he said. “Generally, energy intake must increase by 1 percent for each degree of cold below the LCT.”

Animals fed average- to good-quality hay are more likely to be able to increase intake enough to meet the additional energy demands than those fed low-quality forage, Lewandowski said.

“If poor-quality forage is the only forage option or if there is an extended period of extreme cold weather, then some additional energy supplementation is necessary for the animals,” he said.

Producers should keep in mind that LCT is influenced by an animal’s size, age, breed, nutrition, housing conditions and hair coat or wool thickness. The thicker the hair coat or wool, the more the LCT decreases.

“But with a wet hair coat, regardless of how heavy it is, the lower critical temperature increases to 59 degrees, as hair coats lose their insulation ability when wet,” Lewandowski said, referring to cattle, horses and goats. Sheep wool is able to shed water.

The LCT for beef cattle is 59 degrees during summer or when wet, 45 degrees in the fall, 32 degrees in winter and 18 degrees in heavy winter. For goats, LCT is generally considered 32 degrees and for sheep, 50 degrees.

“For most livestock, it really is a matter of adapting to the weather,” Lewandowski said. “Cattle will adapt to cold with a thicker coat if they have the feed source. And ensuring livestock are blocked from the direct force of the wind will help protect them from wind chill.”

Breeding livestock that are subjected to prolonged periods below their LCT can develop reproductive issues, while other livestock classes will have reduced gains or even weight loss, he said.