Here’s a phrase every Missourian knows and understands: It’s not just the heat, it’s the humidity. While humans can find a way to mitigate rising summer temperatures through a dip in the pool or an afternoon in the air condition, for cattle it merely causes stress.
Jenna Monnig, University of Missouri Extension livestock field specialist, says this is the time of year when cattle producers need to pay extra attention for heat stress in the herd.
“Cattle cannot dissipate heat very effectively compared to other animals, and so are more susceptible to heat stress,” she says in a recent AgConnection newsletter. “They rely primarily on respiration to cool themselves because they do not sweat efficiently.”
Monnig notes that cattle on pasture look for ways to cool themselves like taking to the shade under trees or in buildings. However, those cattle in closely confined areas such as trucks, holding pens and feedlots, or areas without shade access, are more likely to become stressed.
Heat stress can occur any time the temperature-humidity index is above 80 degrees F, or if nighttime temperatures consistently remain above 70 degrees, Monnig says. She warns of heat stress signs: restlessness, decreased feed intake, panting and slobbering. Long-term effects include decreased weight gain and reduced fertility.
Monnig offers the following measures to lessen the impact of heat stress on the cattle herd:
Provide access to water. Be sure cattle have access to plenty of water, as intake will increase during heat stress. Cows need about 2 gallons of water for every 100 pounds of body weight during the summer. Lactating cows need about twice that amount.
Supply plenty of shade. Plan for 30-40 square feet per cow.
Feed in the evening hours. If possible, feed cattle in the evening to decrease heat produced from digestion. Normal digestive processes and fermentation in the rumen create body heat, peaking several hours after consumption.
Avoid working cattle in extreme heat. Core body temperature peaks about two hours after peak environmental temperature and returns to normal four to six hours later. If cattle must be worked, begin in the morning, as soon as daylight allows, and take care to keep handling as low stress as possible.
University of Missouri Extension contributed to this article.