Heat Stress in Livestock Dr.Christine Navarre We are in the midst of heat stress season. High daytime temperatures in combination with high nighttime temperatures and high humidity can be deadly. Heat stress can be a primary disease, causing illness or death. It also can be a subclinical disease causing reduced productivity and suppression of the immune system which makes animals more susceptible to other diseases. Heat stress can cause females to abort and males to become infertile. Heat stress-induced infertility can be permanent, so breeding soundness exams each year on breeding males are essential to make sure they have recovered. Non-heat-adapted males in excess body condition and animals with other health problems (either clinical or subclinical) are at most risk for heat stress. All livestock need adequate shade and unlimited access to fresh, clean water, even heat-adapted breeds. Water should be close to shade. If water is far from shade, animals may not leave the shade to drink, causing dehydration and eventually death. Cool water is best if possible. Water from ponds and lakes gets warm this time of year and does not allow for any cooling effect. Evaporation also can decrease water quality and decrease both feed and water intake. Trough water sources need to have enough capacity to handle cattle numbers, but not so much that water sits and gets hot. Good turnover in a trough will help keep water cool and clean, which encourages water intake and keeps animals cooler. The more mature forages get, the more heat they produce during digestion. Grazing management practices that maximize forage quality also will help combat the heat. Drought The severe drought this year poses several potential problems. •With grass being short, livestock will more likely eat toxic plants. •Blue-green algae in ponds might also crop up. •Body condition scores are likely to drop which has multiple ramifications to health and production. •Early weaning of beef calves, if possible, is a good way to take some pressure off of brood cows.