We’ll go on the assumption that by press time, our weather will change dramatically.
In other words, it will stop raining, the grass will stop greening up, and the temperature will drop below 30 F and stay there.
Even though daily temperatures reaching into the 40s and higher in January are “warm,” adjustments in how we feed calves must be made even when temperatures fall below 60 F.
Background. First, a calf is born with approximately 3 percent body fat. There is barely enough of that fat available to the calf to meet her energy requirements for the first 18 hours of life.
Colostrum has twice the level of fat than normal milk to start addressing the calf’s need for energy at birth.
Second, there is a finite range of temperatures where an animal does not require additional energy to simply maintain the body. In other words, the body functions properly, but neither gains nor looses weight.
Calves are the most sensitive to external temperatures of any bovine age group. Newborn calves (from birth to seven days), have a lower critical temperature around 55 F.
In other words, when the temperature in their environment drops below 60 F, calves require additional nutrients to simply maintain their body weight. After the first week of life, they can handle a few more degrees of cold.
How much? How much extra milk or milk replacer is needed simply to maintain body weight? The following table shows the increasing amounts of 20:20 (protein:fat) milk replacer required to meet maintenance requirements of different size calves at varying environmental temperatures.
Remember, these increases represent maintenance requirements. We also want the calf to grow. Additional milk replacer or milk must be fed to achieve your desired growth rates.
Will it cost more to raise calves in the winter? Yes, but the payoff is having calves that grow and have the body reserves to help them fight bacterial, viral and temperature challenges that come their way.