The dog days of summer apply to cattle, as well as people.
By: Jim Offner, Waterloo-Cedar Falls Courier
Indeed, bovine experts at Iowa State University recently sent out a warning to producers to keep cool heads during the Iowa hot spells, the Waterloo-Cedar Falls Courier reported.
With continuing weather forecasts of temperatures in the mid- to upper 90s and heat index recently eclipsing 100 degrees in Iowa, ISU Extension and Outreach beef veterinarian Grant Dewell sent out a reminder to beef cattle producers that properly preparing for such extreme weather conditions is vital to maintaining herd health.
Heat stress is always a concern, said Jim Thoma, who runs a 1,200-head operation near Jesup.
"In open pens in the sun, it gets pretty bad; it's better to provide shade, especially for cattle that are along in the finishing period," Thoma said. "They have more mega-cals and higher energy rations and are carrying more body fat and there's more to deal with."
Dewell recommended a five-step approach to side-stepping heat stress in a herd: Plan ahead, because after cattle get hot, it's too late for preventative measures. Don't work cattle when it is hot. Provide plenty of fresh clean water. Feed 70 percent of ration in the afternoon. Provide ventilation, shade and/or sprinklers.
"Some guys provide sprinklers," Thoma said. "These newer confinement buildings work probably quite a bit better because cattle are in the shade and if there's a summer breeze it helps a lot. If it's hot, it's going to be hot; you can't control that, but you can kind of control the environment, especially if you have these newer confinement buildings."
Thoma said he has "a couple" of controlled-environment buildings.
Dewell consuming water is the only way cattle can cool down in hot, humid conditions.
"Make sure the water flow is sufficient to keep tanks full, and ensure there's enough space at water tanks — 3 inches linear space per head," he said. "Introduce new water tanks before a heat event occurs so cattle know where they are."
"Heat from fermentation in the rumen is primary source of heat for cattle," Dewell said. "When cattle are fed in the morning, peak rumen temperature production occurs during the heat of day when they can't get rid of it. By feeding 70 percent of the ration in late afternoon, rumen heat production occurs when it is cooler."
"Environmental temperatures compound the heat load for cattle during a heat wave. Remove objects that are obstructing natural air movement. Indoor cattle will benefit from shade provided by the building as long as ventilation is good. Outdoor cattle will benefit from sprinklers to cool them off. Make sure cattle are used to sprinklers before employing them during a heat wave."
Under current management practices, beef cattle and particularly feedlot cattle are most at risk for heat stress, Dewell said.
Cattle deal with stress all summer, anyway, once the temperature rises above 75 degrees, and they have to actively try to dissipate heat, Dewell said.
"When temperature get up in the mid-90s, they have difficulty maintaining their heat balance," he said.
Dewell noted other livestock species — pigs in ventilated buildings and dairy cows in barns with fans or misters, for example — are in more controlled environments.
"Fortunately we don't have heat waves every year," he said, noting Iowa's last major extended heat wave that killed cattle occurred in 2012.
Producers have to protect their herds in winter, but summer can be even more dangerous, Dewell said.
"Typically cattle in Iowa — especially southern Iowa — deal with heat stress more than cold stress," he said.
Thoma said summer is tougher on cattle.
"Other than the way-extremes, like the blizzards, I think the cold is easier to deal with," he said. "Cattle actually like a cold climate. They have quite a winter coat there, and if you keep them out of the wind and the wet in the winter, mostly the wet, you can understand that."
Dave Epley, a cattle farmer near Shell Rock, who has 115 head, plus calves, agreed with Thoma.
"I'd say heat is harder on them, because cold, basically, they just eat more feed and compensate for the extra energy it takes," Epley said.
Epley said cattle will show some signs of heat stress.
"When it gets to the point where the cows are hanging their tongues out and panting like a dog, that's tough," he said.
So far this year, that hasn't happened, Epley said.
Generally, several factors combine to put cattle at risk from heat stress, Dewell said. Among them are temperatures in the upper 90s, with heat indices over 100, with two or three consecutive nights with relatively warm temperatures.
"Normally cattle build up a heat load during the day when it is hot and then dissipate that heat at night when it cools off," he said. "If it does not get below 70 at night they can't dissipate all of the heat so they start the next day with an increased heat load. By the second or third day, some cattle are unable to survive."
The risks are minimized considerably if cattle can cool themselves, Dewell said, noting the biggest issue is decreased performance.
Extra heat typically causes cattle to reduce their intake of feed, and weight gain suffers, Dewell said.
"If the diet is not managed properly, we can sometimes see some ruminal acidosis problems after a heat event," he said. "Cattle have not eaten much for a couple of days, then it cools off and if their return to feed is not managed properly, they can overeat leading to acidosis."
There isn't much that can be done to treat cattle, other than to keep them cool, Dewell said.
"The newer confined barns (monoslopes or hoop buildings) have less of a problem because shade of the roof reduces solar radiation which adversely affects cattle," he said. "If shade is not possible, we recommend using a sprinkler system to keep cattle cool during heat events."
Younger calves are less affected by heat, Dewell said.
"The biggest risk is heavy cattle that are close to the end of the feeding period," he said. "These cattle have more body mass to keep cool and a heavy fat cover that does not allow them to expel heat, as well. Pasture cattle normally do OK; they are freer to find shelter under a tree, stand in pond, etc."
Thoma said size and energy in calves helps them fend off the heat of summer.
"They can deal with it a whole lot better, like your kids," Thoma said. "It's hot for them, too, but they don't have the problems you have with older people, even though they might fuss more."