Jason Hartschuh, Assistant Professor, OSU Extension Field Specialist, Dairy Management and Precision Livestock, Ohio State University Extension
I was slightly more ready for cold weather this year than the last couple. I had the fans taken down so that my calf barn doors would slide shut when the first cold night came around, but still, I was not ready for the dusting of snow I received last week. I was scrambling to make sure my calves would be comfortable. The thermoneutral zone for calves is 50 to 68⁰F, meaning when temperatures in their environment are below the lower critical temperature of 50⁰F, they need extra energy to stay warm. This can be a challenge since 50⁰F at night often has highs of 70⁰F during the day. Usually, calves deep bedded with straw manage this variation by nesting with their legs covered at least to the middle of the back leg when lying down. The next step is adding calf jackets to help keep calves warm. 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 prematurely, putting the jacket on at night and taking it off during the day is extra work but may help calves that cannot regulate their body temperature very well. The calf jacket material should be breathable with a water-resistant shell. It is recommended that producers start using jackets once the 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 is higher as the calf’s rumen develops, creating heat to keep them warm. 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 to quickly dry the calf.
When calves are first born and they start shivering, they are burning precious energy. 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 increase growth, more milk solids have to be fed but solids concentration should not exceed 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 82⁰F to calves within 30 minutes of finishing their milk. Water intake improves starter intake by 31%. However, it lowers their rumen temperature, requiring energy to warm the water and even more energy to maintain weight and allow for growth.
Pay close attention to winter ventilation, keeping barns or hutches warm is not the goal. Keeping the 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 windbreaks or temporary windbreaks, 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. Having written ventilation protocols for your calf barn and hutches along with thermometers placed both inside and outside your calf-raising area can help everyone remember to make the necessary ventilation adjustments as day and nighttime temperatures fluctuate.