Signs of heat stress (depends on species) may include animals bunching, seeking shade, panting, slobbering or excessive salivation, foam around the mouth, open-mouth breathing, lack of coordination and trembling.
If these symptoms are observed, assume the animal has a heat load. Immediately try to minimize the stress to the animal, especially its handling or movement. Previous health of individual animals is an important risk factor; animals that have had past health problems will be more affected by heat stress than animals with no prior health problems.
These animals will generally be the first to exhibit signs of heat stress and be the most severely affected. Hot weather and high humidity can reduce feed intake, weight gain, reproductive efficiency and milk production, while increasing susceptibility to disease. Changes in the animal’s behavior and even death can also occur.
The comfort zone for animals varies depending on age. Young animals generally have a narrow comfort zone between 45°F and 80°F; while the range in temperatures of the comfort zone of mature animals can be wider. For example, with feedlot animals and mature cows the comfort zone can range from below zero in the winter to about 75°F in the summer. Bos indicus (humped cattle) do have better heat coping capabilities and can easily tolerate temperatures above 90°F.
Normally, you find Bos indicus cattle in the southern parts of the United States. Environmental stress is dependent on temperature, humidity, wind speed and solar radiation, which is best determined by an index. The index that is most commonly used is called the Heat Index, commonly reported by many media outlets during the summer. Establishing good management options is very vital when tending to livestock during hot weather.
Management options include providing shade, ventilation and air flow, clean and cool water, wetting, cool water drench and sprinklers or hoses.
• Shade can be provided by trees, buildings, or other sunshades. In addition, the temperature can be lowered by spraying cool water on the roof and walls of buildings where animals are being housed.
• Improved ventilation can be provided by fans or opening windows on a breezy day. Sunshades should be high enough off the ground (10 feet or more) to allow for adequate air movement.
• Clean and cool drinking water is essential to keeping the animal’s internal body temperature within normal limits. Providing cool drinking water will help cool the animal’s core. If water space is limited, provide additional portable water troughs.
• Wetting is a good way to cool an animal suffering from heat stress. The animal should be gradually wetted with cool water; avoid excessive cold water for this purpose. Gradual wetting may need to be repeated until the heat stress symptoms have dissipated.
• Cool water drench (administer orally) may help quickly decrease the animal’s core temperature. Method should be performed by someone who has experience in drenching an animal.
• Sprinklers or hoses can provide some relief to heat-stressed animals. The water droplet size should be large; misting (small droplets) may only add humidity and moisture to the air. Keep in mind if animals are not acclimated to sprinklers, they may become frightened, which will add to their stress level.
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