If there is a drawback to fall calving, it is summer weaning. Calves are under enough stress as it is. Add summer heat and humid

News
Jul 29, 2011
by DTN

If there is a drawback to fall calving, it is summer weaning. Calves are under enough stress as it is. Add summer heat and humidity, and you’ve got the potential for real trouble.

“Stress is cumulative,” says Max Irsik, University of Florida Extension beef veterinarian. “The stress from moving the calves, handling them, vaccinating them, heat stress … it can take three weeks for their immune systems to get back to normal.”

John Harrison agrees weaning and heat are a good way of doubling your problems. The Cairo, GA, producer schedules for an October through December calving season, but that means he weans in June and July. And it doesn’t help that cattle are designed without a good radiator.

“They don’t sweat,” Irsik says. “They either have to radiate heat out of their bodies or their respiratory system. They also have a large rumen that is nothing more than a fermentation vat. It acts as a heat pump.”

Temperatures don’t even have to be that high to put calves at risk. If humidity levels are up to 60 percent and it is 85 F (or any combination that raises the temperature humidity index to 79), conditions can put calves in the danger zone. And a heat-stressed bovine is easy to spot.

Irsik says, “They sling their heads, lick themselves and hang their tongues out. They pant, drool and stick their heads out so the air passage has the least resistance. Their core temperature goes up, and they can get in a hyperthermic condition. When they do, there isn’t a lot you can do about it. They can die.”

While you can’t change the weather or redesign cattle, there are practices to minimize the effects of heat stress at weaning.

Fenceline weaning

At weaning, Harrison puts calves in a small, familiar pasture and simply moves cows to an adjoining pasture. They’ll sniff each other through the fence. It takes about three days for the calves to stop bawling and fence walking. At that point, they are moved to a millet pasture.

“Fenceline weaning is definitely less stressful on calves,” Irsik says. “I would think in some cases it would help calves deal with heat stress.”

Well-placed feed and water troughs

Calves aren’t going to eat and drink like they should because they are walking the fence looking for their mamas. Therefore, dehydration can be a factor.

Calves generally need two to three gallons of water per 100 pounds of body weight a day.

Harrison says he tries to avoid dehydration by putting feed troughs on the fenceline and a water trough at each end of the lot. “They can’t help but find the feed and water when they are walking the fence,” he says.

A source of shade

Shade is the biggest thing when the summer sun is beating down and humidity levels are climbing. Harrison says trees shade both the small pasture he uses to wean his home-raised calves and the lot he uses for his custom preconditioning calves. He also keeps the lot size down for customers’ calves to minimize pacing and walking.

Three acres for 40 to 50 calves is typical, he says.

Vaccination timing

Vaccinations and weaning used to be handled at the same time at Harrison’s farm, but he’s got new ideas about that.

“Now we try to vaccinate three weeks ahead of weaning time,” Harrison says.

“That cuts down on the stress at weaning. Those blackleg shots are tough on them.” He gives booster vaccinations a week after weaning when calves have had a chance to settle down.

Harrison’s neighbor, cattleman Caylor Ouzts, has a similar strategy for his fallborn calves. “We do all our vaccinating and castrating while they are still on the cows. It is too stressful to vaccinate them when we wean.”

He also waits to give the second series of vaccinations until two or three weeks after weaning. And when he and Harrison do their post-weaning vaccinations, they agree the key is to start first thing in the morning and try to finish before it gets too hot.

Breed for heat tolerance

Harrison has a purebred and commercial Hereford operation. Red cattle have a reputation for handling heat better than black cattle, but he goes a step further. After a round of AI using semen from purebred Hereford bulls, he turns in Brahman bulls to clean up. “The Braford calves never go in the shade,” he says.

Ouzts’ calves are Angussired and black, but he is careful to keep one-quarter Brahman blood in them. “That is perfect for down here,” he says.

Measure heat stress

While there is nothing you can do about the weather, in some cases you can plan weaning around it. There are several online tools to help at www.ars. usda.gov/Main/docs. htm?docid=21306. Here you can find a seven-day forecast specifically looking at heat stress potential. The site also lists environmental and animal factors that contribute to heat stress.

At www.noble.org/Ag/ Livestock/Heat/ you will find a livestock weather hazard guide for beef cattle based on temperature and humidity. — DTN

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