It is time to change to winter bedding and bring out the calf jackets to provide calves extra warmth from low temperatures.
If you normally use shavings as calf bedding during summer, it is now time to switch to straw bedding to help keep calves warm. Michigan State University Extension recommends using straw bedding when temperatures are 40 degrees Fahrenheit or below. Straw bedding is ideal when daytime highs or night time lows are below the thermo-neutral zone for a young calf. A newborn Holstein calf has to burn energy to keep herself warm when temperatures are below 50 F. If there is draft, wet bedding, or an immune system challenge, then the critical temperature is higher.
A calf is born with only 2-4 percent of body weight as fat, which will not last long if she is forced to burn fat for heat production. Burning body fat for heat can lead to lower growth rates, compromised immune status, and even death. The need for straw bedding at this time of the year to provide warmth for young calves is true both in barns and in hutches. Unless the calf barn has supplemental heat, it should be well ventilated, but without drafts on the calf, and within 5 degrees of outside temperatures, necessitating the use of straw bedding and calf jackets.
Straw is the best choice of bedding to provide thermal insulation for the young calf. Straw tends to hold moisture, so it is important to add fresh bedding regularly. Moisture exceeding 20 percent is too high. If you kneel with all your weight in the calf bedding, any moisture on your pants indicates the bedding is too wet. Straw should be bedded deep enough that the calf can nestle in. This traps warm air around the calf, which will help maintain body heat. For winter months, the straw should be deep enough that when the calf is lying down its legs are generally not visible.
Calf jackets are another way to protect calves from losing excess body heat. A field trial from North Dakota State University found that calves housed in hutches during winter had higher average daily gains when wearing calf jackets. Gains for jacketed calves averaged 1.15 pounds per day for the first three weeks of life, while calves without jackets averaged 0.82 pounds per day. When using calf jackets, ensure that they are sized correctly and stay dry.
The use of deep straw bedding and calf jackets during low temperatures will help young calves stay warm resulting in improved average daily gains and immune status.