A beef and forage specialist at the Alberta Ag-Info Centre, Barry Yaremcio, says there's a limit to the amount of heat cattle can produce by digesting feed so adjustments need to be made.

"Cattle can stay warm down to -20 C without wind chill, and the heat from digestion when they consume their feed will keep them warm. I am referring specifically to cattle, but these principles apply to other animals that are staying outside," Yaremcio says.

He says it's a natural response for animals to eat more feed when it gets cold and suggests providing extra hay or silage along with extra grain.

"You can't just let them pick extra hay or pick straw off the bedding pack to make up the intake differential," he adds. "Straw is a low protein, high fibre, low energy feed that takes a long time for the animals to digest. If they eat extra straw, the total protein content in the ration goes down, and bacteria can't digest the fibre. In reality, their feed intake, in reality, may drop 2, 3 or 4 pounds a day, and the animals will drop condition by eating only extra straw."

At -30 C, he says to increase grain intake by an extra 2 lb of grain per head per day over and above what was previously being fed at -20 C. If temperatures drop to -40 C, 4 lb of extra grain per head per day needs to be added.

Providing shelter behind a wind fence and providing a lot of bedding helps reduce the amount of energy needed for an animal to keep warm.

"A cow laying on snow could potentially lose 25% of her body heat, especially if that snow is wet or the animal has a dirty hair coat," he says. "During cold weather, cows can lose anywhere between 1 to 3 lb a day. If the cow is losing weight in the last trimester of pregnancy, there could be more calving difficulties because the cow’s muscles are not as strong as they should be. Nutrient requirements for a lactating cow increase by 25% compared to one in late pregnancy. That is when the large weight losses can occur."