Calves are most comfortable when outside temperatures are between 50 and 68 degrees Fahrenheit – a calf’s thermoneutral zone. At less than 50 degrees calves need extra energy to stay warm. Farmers can help manage calf health and well-being in cool weather.
But that can be a challenge when nighttime temperatures are 50 degrees and daytime temperatures exceed 68 degrees. Calves provided deep straw bedding manage temperature variation by nesting with their legs covered, at least to the middle of their back legs.
As temperatures cool, adding calf jackets can be beneficial. Studies show that calves provided jackets can improve gain by .22 pound per day compared to calves not provided jackets. But adding jackets when it’s warm may cause calves to sweat and become chilled at night.
Supplying a jacket to a premature calf at night and removing it during the day is extra work but may help calves that can’t regulate temperature well. Calf-jacket material should be breathable with a water-resistant shell. Producers should provide jackets to calves to three weeks of age once pen temperature averages less than 50 degrees. After that calves are comfortable until average pen temperatures are cooler than 40 degrees.
The critical temperature continues to decrease as a calf’s rumen develops; it creates heat to keep the animal warm. Calves that aren’t eating much starter grain may be uncomfortable at reduced temperatures due to less rumen activity.
Calf jackets should be dry. That means calves should be dry before they’re supplied a jacket. Use clean towels to dry calves. When calving-barn temperatures are 40 degrees or less, have towels available in a calving-pen cabinet. Putting calves in a warm room or calf warmer also can help.
Warm air they breathe warms their insides but be sure it’s ventilated well so calves fully dry within a couple of hours. Air quality can become poor enough to cause pneumonia. When calves are first born and start shivering, they burn precious energy. A newborn has about 18 hours of brown-adipose tissue reserves, making colostrum extremely important. Shivering calves can burn though the reserves even faster.
For each 1 degree decrease in temperature to cooler than the critical temperature, a calf needs a 1 percent increase in energy to meet maintenance requirements. There are many different calf-feeding programs. But milk solids must be fed without solids concentration exceeding 16 percent. The most common way to increase energy intake is to feed either more per feeding or add a third feeding. Eight hours apart is ideal for three feedings, but the most important point is to make timing consistent. Feed the same amount at each feeding even if that means adding a lunch feeding between normal feeding times.
Another beneficial practice is to provide calves warm water at 63 to 100 degrees within 30 minutes of finishing their milk. Water intake improves starter intake by 31 percent. Calves are then better able to stay warm as their rumen digests grain. Cool water may improve starter intake but it reduces rumen temperature, requiring energy to warm the water and even more energy to maintain weight and allow for growth.
Pay attention to winter ventilation; keeping barns or hutches warm isn’t really the goal. Instead the goal is keeping air fresh to minimize disease while not allowing drafts on calves. With hutches that usually means having either permanent winter wind breaks or temporary wind breaks such as straw bales. Winter winds seem to change and bring cold weather from every direction. In calf barns pens are a microenvironment affected by ventilation and design. Studies have found that solid sides slow disease spread but are beneficial only if the front, back and top of the pens are open. Otherwise they create a microenvironment for disease. A properly designed positive-pressure tube providing ventilation at a rate of 15 cubic feet per calf per minute can improve calf health without creating a chill.