It could be for short or long durations and possibly at the most inopportune times. Much research is still being conducted on how animals perform in hot climates and how heat stress impacts productivity.
Ideally, we try to avoid working cattle during excessive heat. Working animals in the morning is best. Although evening has a cooler ambient temperature compared to the extreme of the day, the animal’s core body temperature will still be hot for at least a couple of hours beyond peak high temperature. Cattle not only have limited ability to cool themselves but also have heat being produced from rumen fermentation. Some suggest feeding or rotating pastures in the evening so the bulk of fermentation heat tapers off by the following day’s hot period.
Cattle need to have an abundance of available shade. Sufficient space is helpful to reduce crowding and allow better air flow. Fly control is also helpful to reduce crowding. Access to clean, abundant water is essential. In times of high heat, there tends to be reduced rainfall. Be watchful of ponds developing toxic algae. As a side note, greater water consumption increases mineral consumption.
Hide color, breed influence and regional adaptation also play a large factor in managing heat stress. Bos indicus cattle account for most of the world’s cattle population, as they make up the bulk of the cattle in the tropical and subtropical climates of the world. The hotter the climate, the more Bos indicus influence is needed. The lower portion of the Southeast falls into the subtropical portion and thus can greatly benefit from a 1/4 or 1/16 of Brahman influence.
More extensive sweat glands combined with loose skin, short hair coat, skin pigmentation and a lower internal body temperature allow Brahman- and Nelore-influenced cattle to thrive in hot and humid climates. It is well understood that they are adapted to temperatures over 105ºF with almost no impact on production. Bos taurus breeds developed in the South with selection for heat tolerance and short hair coats obviously have an advantage over herdmates developed in colder climates. 
-
Jason Duggin
- Beef Extension Specialist
- University of Georgia
- Email Jason Duggin
