“Heat Stress Abatement: Prevention IS the Cure”
by Chris Reinhardt, feedlot specialist
When we consider true heat stress and the potential for damaging impacts, we must consider the “Effective Ambient Temperature” which is made up of actual dry-bulb temperature and humidity. But we must also factor in average wind speed (or lack thereof). 95° in Garden City is by no means the same as 95° in Chanute. The difference? Humidity and wind.
Heat-stressed cattle will seek out higher elevations to catch a breeze in order to unload heat. Proper design of mounds within pens can help. Cattle can tolerate a fair bit of heat accumulation during the day, provided they can unload that heat during the evening and nighttime hours. But if the effective ambient temperature (“heat index”) doesn’t fall below about 80° at any point during the night, the cattle will go into the next morning carrying heat from the previous afternoon. And if the subsequent day has similar conditions, the heat load building in the cattle will increase to critical levels.
Black-hided cattle are at much greater risk of devastating heat stress due to the amount of solar radiation absorbed by their dark hide. White or light colored cattle rarely suffer as greatly as black cattle during extreme heat situations. Shades will reduce radiant heat accumulation, but it is important that the shade design not stifle air movement.
The most important factor under your control in preparing for heat stress conditions is sufficient water space and capacity. During the summer months water intake not only increases, but the majority of that increased demand is focused around the mid-afternoon hours. In anticipation of extreme heat events, it is important to have large water tanks available and filled. This will give more cattle a place to drink as well as relieving some of the strain on water flow capacity.
Sprinkling can also alleviate heat during the most extreme conditions. A critical element in maximizing the benefits of sprinkling is making sure the spray consists of large, heavy water droplets. A fine mist will evaporate making air more humid, but large droplets penetrate the hair coat to the surface of the skin maximizing the evaporative cooling benefit.
