Keeping water lines thawed and moving snow aren’t the only extra tasks that Old Man Winter creates on the dairy. Carefully managing calf nutrition is another demand that requires attention during the frigid winter months.
“Newborn calves start out life with very minimal energy reserves,” says Mike Van Amburgh, associate professor of animal science at Cornell University. “Because calves have a higher surface-area-to- bodyweight ratio than older animals, they become cold-stressed at fairly moderate temperatures.”
He explains that at temperatures below the “thermoneutral zone,” calves start to expend their internal energy reserves simply to maintain their core body temperature of 102 degrees F. The result: energy resources are diverted from growth and immune function, meaning calves will not gain weight, and are more susceptible to diseases like pneumonia and scours.
Van Amburgh says the thermoneutral zone for Holstein calves three weeks of age is 68 degrees F to 82 degrees F, but at temperatures below 60 degrees F, calves have to increase energy expenditure to maintain body temperature. For calves from 22 days of age to weaning, it is approximately 42 degrees F, depending on insulation and rumen function. “When an 88-pound newborn calf has to start mobilizing its own fat stores to stay warm, it has less than one day’s worth of energy ‘in the bank,’” he notes.
Colder weather demands higher nutrition
To help calves survive and thrive in cold weather, diet is the first line of defense. Because young calves three weeks and under have little to no rumen function yet, nearly all of the required extra energy must come from a liquid feed source.
Whether milk replacer or pasteurized waste milk is the primary liquid feed source, calves will use more energy when temperatures drop. Van Amburgh says a traditional milk-replacer program of feeding 20 percent protein, 20 percent fat milk replacer at a rate of 1 pound of dry powder per day (2 quarts of milk replacer fed twice a day at standard dilution rates) will result in strictly maintenance for the calf, with no remaining energy for weight gain at temperatures below the thermoneutral zone.
Pasteurized whole milk fed at the same volume will provide 11 percent to 18 percent more energy due to its higher protein and fat content. However, consistency of nutrient levels in whole milk can vary considerably day-to-day, which requires careful monitoring of this feed source. Increasing nutrient levels in whole-milk feeding programs to accommodate for colder temperatures also may require supplementation with milk replacer, depending on the volume of waste milk available on the dairy.