Regular feed only goes so far in keeping cattle warm when it’s bone-chilling cold.
“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,” said beef and forage specialist Barry Yaremcio.
Feed requirements change when it gets that cold.
“You can’t just let them pick extra hay or pick straw off the bedding pack to make up the intake differential,” he said. “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.
“Their feed intake in reality may drop two, three or four pounds a day, and the animals will drop condition by eating only extra straw.
“At -30 C, increase grain intake by an extra two pounds of grain per head per day over and above what was previously being fed at -20 C. If temperatures drop to -40 C, four pounds of extra grain per head per day needs to be added.”
Thin animals get cold faster than those that are in good shape, so they may need six or seven pounds a day to maintain their body weight.
Protein content is also important.
“If the ration’s protein content is not adequate, the microbial populations cannot reproduce efficiently, as some of those microbes are needed to digest the fibre in the feeds,” said Yaremcio. “If the fibre is not digested efficiently, feed intake will be reduced, restricting the amount of nutrients the animal is getting.”
One way to evaluate the protein content of the ration is to look at the manure.
“If the ration contains adequate amounts of protein for proper rumen function, the ‘pats’ will be flat and appear normal. If the ration is deficient in protein, the pats will be more pyramid shaped and be rough in appearance.”
Providing shelter behind a wind fence and providing a lot of bedding helps, but if possible, the thinnest animals should be moved into a barn.
“A cow laying on snow could potentially lose 25 per cent of her body heat, especially if that snow is wet or the animal has a dirty hair coat.”
Failing to reduce stress from cold temperatures could compromise the animals.
“During cold weather, cows can lose anywhere between one to three pounds a day,” said Yaremcio. “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 per cent compared to one in late pregnancy. That is when the large weight losses can occur.”
There are many issues if a cow is losing weight prior to calving, he added, including reduced quantity and quality of colostrum, reduced milk production, and calves that are more susceptible to disease and may have a slower rate of growth.