HEAT-STRESS IN FEEDLOT CATTLE

Heat stress occurs when the heat load of feedlot cattle is greater tha n heir ability to lose heat. Feedlot performance of cattle is reduced during periods of heat stress because maintenance requirements increas e while the animal's appetite is decreased. Overheated cattle pant to cool themselves, thus decreasing the amount of time they spend eating or ruminating. Also, fermentation of ingested feedstuffs increases the animals' heat load. Cattle also perspire to cool themselves. During p eriods of heat stress, cattle lose large amounts of potassium in sweat . The potassium as well as the sodium content of the ration should the refore be increased during hot weather. The veterinarian should advise the producer to be prepared to minimize the adverse effects of heat s tress on cattle by altering the microenvironment with facility modific ations and various management practices. The following measures have b een used to reduce heat stress in feedlot cattle: provide the correct water facilities, adjust rations, handle cattle correctly, use shades and sprinkler systems, and choose cattle by type and origin. When temp erature coupled with humidity reaches high enough levels, the problem may no longer be keeping cattle cool but keeping them alive.