It seems like we have missed a transition period on the temperatures and went straight from nice and 75 degrees to a scalding 90 degrees. These hot temperatures are not only hot on us, but it can be detrimental to your cattle.
Anyone who has ever burnt their forearms by leaning on the hood of a truck knows how hot things can get while out in the blistering sun. Cattle are no different, especially since most of our cattle are black. Cattle are not only affected by the heat from high temperatures and humidity, but they also create their own heat through metabolism and body movements. These conditions add up to a reduction in performance, if not managed properly.
I know that when I get really hot, the last thing I want to do is eat. The same is for cattle. As temperatures rise, dry matter intake decreases. Research has shown that if temperatures are 95 degrees F or above with some nighttime cooling that DMI could decrease up to 10 percent, and if it is 95 degrees or above with no nighttime cooling that DMI could decrease to 65 percent of normal consumption. At the same time, not is DMI decreasing but the animal’s maintenance requirement is increasing due to body temperature regulation (panting).
Heat stress on a bull can severely affect your herd’s pregnancy rates. Hot weather can decrease the quantity of sperm a bull produces and a longer recovery time to normal levels of semen production. A study conducted by OSU heat stressed some bulls by placing them into a temperature controlled room (eight hours at 95 degrees and 16 hours at 88 degrees each day). These bulls were kept for eight weeks and then the heat stress was removed and the temperatures were changed to 73 degrees for another eight weeks. The study showed a statistical reduction in sperm motility at the second week. By the eighth week, sperm motility had been reduced to below 50 percent. Once the heat stress was removed, it took the animals eight weeks to recover back to a normal sperm motility. Not only does heat reduce the quantity and quality of sperm but it also reduces the bull’s libido. One study showed a 48 percent reduction in bull mounts during the summer versus winter.
There are a few things we can provide our animals with that may not eliminate heat stress but help reduce the unpleasantness of it.
•Shade — Natural or manmade, adequate shade will help reduce the effects heat stress.
•Minerals — Increased heat brings increased water intake. This increase in water intake will increase urine production, which increases mineral excretion.
•Fly Control — Controlling flies will help reduce the animal’s activity.
•Sprinkler — By using large droplets (not a mist), wetting animals to the hide will help the animal cool down. Once you start with sprinklers, you must continue until the heat wave has passed.
These are just a few options to consider during the hottest times of the year. Other resources we can use as tools to determine when our animals are stressed are www.ars.usda.gov and www.mesonet.org for heat stress forecast. If you need more information on ways to manage heat stress on cattle, please visit your OSU Extension office. £
(Source: Oklahoma Cooperative Extension Service - Northeast District’s Timely Topics)