If you find heifers not gaining as much weight as you planned due to cold stress, use the following steps to change their environment and their diet.
1. "Micro-manage their environment," suggests Pat Hoffman, dairy scientist with the University of Wisconsin. Make sure resting areas have ample bedding. Younger calves need an insulated type of bedding, such as straw, he says. You may want to avoid sand because it lacks thermal qualities.
Look at the mud and manure cover on heifers. Does mud or manure cover their flanks, abdomen and sides? How deep is the manure on the pack? Could more frequent cleaning result in a drier hair coat?
2. Next, increase the energy available in the ration. Many ration-balancing programs allow you to adjust for seasonal factors. Hoffman recommends that you adjust the energy portion of the ration for a rate of daily gain 0.2 to 0.3 pounds higher than desired. For example, if you want heifers to gain 1.7 pounds per day, provide enough energy for 1.9 or 2 pounds per day.
3. Be prepared for increases in intake. The colder temperatures drop, you may find heifers eating more. Research at Virginia Tech found that heifers began to eat more when temperatures fell to 10 F or below for several days.
For example, heifer growers Melvin and Sharon Neimann, Edgar, Wis., raise 1,700 heifers in an outdoor mounds/windbreak system. With no barn for cover, the Neimanns' heifers experience cold stress more than those housed in conventional facilities. "We find the dry matter intakes increase by around 15 percent in cold conditions," says Sharon Neimann.
Monitor intakes closely and maintain a 1 percent to 2 percent refusal rate. "This may not be the time of year to limit- feed heifers," says Bob James, dairy nutritionist at Virginia Tech. Limit-feeding, or providing heifers just enough feed, doesn't give you clues that the animals need more energy.
4. Measure as you go. Getting the desired rate of gain in cold conditions takes tinkering. You may need to adjust the ration and then weigh heifers to see if it's working.