When you’re working on next year’s calf crop, it’s important to manage the heat.
“We know that the conception rates of cows bred right before, or just during, high, stressful heat times will be compromised anywhere from 10-50 percent,” Eldon Cole, University of Missouri Extension regional livestock specialist at the office in Mt. Vernon, Mo., told Ozarks Farm & Neighbor. He explained that when the cow’s body temperature rises, her body will attempt to reduce the expected burden of a newborn by aborting or reabsorbing the developing embryo or fetus. It’s particularly severe when the cow’s consumption of endophyte-infected toxic fescue elevates her temperature into the 104-6o F range.
Part of the solution is plenty of shade and water – “not necessarily cold water,” Cole said. “Cattle don’t seem to prefer cold water, and in fact may prefer more middle-range temperatures.” But water needs increase drastically when the temperature rises into the 80s, and humidity is in the 60-70 percent range. The source of shade can vary, but Cole said a study in Arkansas showed, “There’s nothing that’ll beat a nice, big old tree, with space under it for cattle to be able to loaf underneath the tree and get out of the direct rays of the sun. Portable shades carry the risk that cattle will crowd up and block the breeze. He said even feedlots, which for many years never worried about the effect of heat on cattle performance, are now talking about installing sprinklers or shade. For confined animals, better air movement is also a plus.
Diet is also a concern, but Cole said it’s a misconception that a diet high in corn or other concentrated feedstuffs makes the animal uncomfortable. He said, “There’s probably more heat that develops as a result of the process of rumination on a high roughage diet. A beef cow, of course, is not going to be getting much concentrate. Toxic fescue is another issue; it impairs circulation, causing the cattle to develop long, shaggy hair coats that further raise the cow’s temperature in the summertime.
“One of the practices that we try to put into place with managing heat stress is getting cattle off of fescue during the middle to latter part of the breeding season, when fescue is getting mature and we’re starting to get elevated daily temperatures,” said Dr. Shane Gadberry, professor of animal science with University of Arkansas Extension. “The other aspect of managing for heat stress is looking at your breeding season. We really try to encourage cattle producers to have controlled breeding seasons that complement the forage growing season, and try to stay away from exposing cattle to breeding during the months of July and August here in the Ozarks.”
Although it’s generally too costly for a cow/calf producer to replace an entire toxic fescue stand with one of the novel non-toxic varieties, replacing a portion of the pasture could be an option. Gadberry pointed to research by his colleague, Dr. Ken Coffey, who compared performance of cows on 100 percent Kentucky 31 tall fescue to cows on pastures where 25 percent of the area was replaced with a non-toxic variety; the latter group, which included both fall and spring calving cows, was placed on the novel variety for four weeks prior to breeding and during the first three to four weeks of the breeding season. The spring-calving cows bred on non-toxic fescue had 82 percent higher calving rates, and their calves weighed 29 pounds more at weaning compared to spring-calving cows on 100 percent KY 31.
The inability of the cows to dissipate due to fescue toxicity, noted Gadberry, is the biggest problem; it can even hamper development during more temperate times of year. He said, “We’ll get into a situation where in the early spring the daytime highs are in the 60s and those cows should still be in a thermal-neutral environment – they haven’t exceeded their upper critical temperature. But we’ll still find those cattle in ponds during the spring.”
