Jim Dickrell is the editor of Dairy Today and is based in Monticello, Minn.
Jun 01, 2012
It’s the beginning of summer and the living is easy. Unless, of course, you’re a cow.
High milk production plus even moderate temperatures (think 70°s) equal the beginning of heat stress. A presentation by Jim Spain at the Minnesota Dairy Health Conference a couple of weeks ago drove home the point.
Spain is a dairy specialist at the University of Missouri. Environmental chambers at Mizzou allow dairy scientists to test heat stress quickly. Some bullet points:
• If you can do no other cooling, do so in the holding pen—and every time cows come through when the temperature-humidity index exceeds 73. That will ensure cows will be cooled at least twice daily (three times if you milk 3X). The holding pen is also where cows can experience the most heat stress each day as they crowd together and share their body heat.
• Leave freestall fans on overnight. Cows reach peak core body temperatures between 8 p.m. and 2 a.m. “It takes four hours of fan cooling time to bring those temperatures down. So why do we turn fans off at night?” asks Spain.
• There’s a belief that if you place fans at the feedbunk, cows will stand at the bunk and eat more. Spain says cows will stand at the bunk longer under fans, especially if the freestalls don’t have fans. But research shows they won’t eat any more. All they’re doing is standing more, which only leads to more lameness.
• If you have to prioritize where you place fans—a choice between the feed line and freestall beds--place the fans over the beds. The reason: Cows spend—or should spend—more time resting in the freestalls than standing at the feedbunk.
• Position fans so that they blow air over the entire cow. If you simply place fans down the center of the freestalls in head-to-head rows, you’ll only cool the cows’ heads and lose the cooling effect on the cows’ bodies. The cow’s large body mass is where you need to direct cooling.
• Cool close-up cows because they are especially susceptible to heat stress. “The fetus produces substantial heat due to the very high metabolism rate associated with fetal tissue growth and development,” Spain says.
One of the best ways to cool close-up cows is to run them into the holding pen during down times. It often has the best fans on the farm, and if the pen isn’t crowded, can provide substantial relief for close-up cows.
At Missouri, researchers sprinkled close-up cows twice a day—7 a.m. and 7 p.m.--until their skins were wet. Then they ran fans for at least an hour. Milk production was 5 lb./day higher for the first six weeks after calving for these cooled cows. Other research has shown cooled close-up cows breed back sooner with fewer services per conception.
If you can’t soak cows or provide fans, try to at least provide shade for dry cows, says Spain.
• Finally, calves in hutches need shade cloth over the hutches. Research at Missouri shows temperatures in a hutch can be 10° higher on the inner surface of the hutch if it is not protected by shade. “Rectal temperatures and respiration rates of the calves in the shaded hutches was significantly lower,” he says.
Read more on cow cooling here
and more on calf cooling here