Jason Hartschuh, Extension Educator, Crawford County, Ohio State University Extension
Winter roared in this year way before most of us were ready. Corn still in the field, barn doors not dug out and winter calf supplies still in the back corner of the barn. Even though we know winter is coming, it never seems like we are ready when the first blast of winter comes.
Calves are most comfortable when the outside temperatures are between 50 to 68⁰F, which is a calf’s thermoneutral zone. When temperatures are below the lower critical temperature of 50⁰F, calves need extra energy to stay warm. At times during winter, this can be a challenge since 50⁰F at night can have highs of 70⁰F during the day. Usually calves deep bedded with straw manage this variation by nesting with their legs coved at least to the middle of the back leg when lying down.
As temperatures continue to fall, adding calf jackets to help keep calves warm will be beneficial. Studies show that calf jackets improve gain by 0.22 lb/day compared to those without jackets. Adding jackets when it is warm out may cause the calves to sweat under the jacket and get chills at night. If you have a calf born premature, putting the jacket on at night and taking it off during the day is extra work but may help calves who cannot regulate temperature very well. Calf jacket material should be breathable with a water resistant shell. It is recommended that producers start using jackets once pen temperature averages less than 50⁰F for newborn calves up to 3 weeks old. Once calves are over 3 weeks of age, they are comfortable until average pen temperatures are below 40⁰F. The lower critical temperature continues to decrease as the calf’s rumen develops, creating heat to keep them warm. Calves who are not eating as much starter grain may not be comfortable at these lower temperatures due to less rumen activity. One important management step with calf jackets is to keep the jackets dry, which means calves should be dry before putting jackets on. If the calf is still damp, you will need to change jackets after a few hours. In order to put jackets on dry calves, you should have clean towels to dry the calves.
One thing that works very well when calving barn temperatures fall below freezing, or even 40⁰ F, is to have towels in a cabinet in the calving pen to help the cow dry the calf quickly. Putting calves in a warm room or calf warmer can also help warm and dry them off. The warm air going in their lungs warms the insides but be sure it is warm enough and ventilated well so that the calf fully dries within a couple hours. Poor ventilation leads to the calf not drying and air quality becoming poor enough to cause pneumonia. When calves are first born and they start shivering, they are burning precious energy. A newborn calf has about 18 hours of brown adipose tissue reserves, making colostrum extremely important. Cold shivering calves can burn though these reserves even faster.
For each 1 degree drop in temperature below the lower critical temperature, a calf needs a 1% increase in energy to meet maintenance requirements. There are many different calf-feeding programs. With all programs to continue growth, more milk solids have to be fed without solids concentration exceeding 16%. The most common way to increase energy intake is to feed either more per feeding or add a third feeding. While 8 hours apart is ideal for three feedings, the most important part is to make timing consistent. Feed the same amount at each feeding, even if that means adding a lunch feeding between your normal feeding times.
Another beneficial practice is to provide warm water at 63 to 100⁰F to calves within 30 minutes of finishing their milk. Water intake improves starter intake by 31%. These calves are then better able to stay warm as their rumen digests the grain. Cool water may also improve starter intake but it lowers their rumen temperature, requiring energy to warm the water and even more energy to maintain weight and allow for growth.
Close attention needs to be paid to winter ventilation; keeping barns or hutches warm is not really the goal. Keeping air fresh to minimize disease while not allowing a draft on the calves is the goal. There are many ways to do this. With hutches, it usually means having either permanent winter wind breaks or temporary wind breaks, like straw bales. Winter winds seem to change and bring cold nasty weather out of every direction, even the south. In calf barns, pens are a microenvironment affected by ventilation and pen design. Studies have found that solid sides slow disease spread but are only beneficial if the front, back, and top of the pens are open; otherwise, they create a high disease microenvironment. When disease and ventilation are challenging your calves, a properly designed positive pressure tube providing ventilation at a rate of 15 cubic feet / calf / minute can improve calf health without creating a chill.