Hay Bales: Managing heat stress in livestock

Mike Trammel, ag educator and multi-county agronomist
Pottawatomie County Extension Service

Depending on the animal, signs of heat stress may include bunching, seeking shade, panting, slobbering or excessive salivation, foam around the mouth, lack of coordination, and trembling. If these symptoms are observed, assume the animal is suffering from heat stress. Immediately try to minimize the stress to the animal, avoid handling or movement. Previous health of individual animals is also an important risk factor. Livestock that have had past health problems will be more affected by heat stress than livestock 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, change in an animal’s behavior or even result in death. 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 mature animals can be wider. For example, with feedlot animals and mature cows the comfort zone can range from below 0°F in the winter to about 75°F in the summer. Bos indicus or humped cattle, such as Brahman 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 also plays a role and 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. The Oklahoma Mesonet product, cattle comfort advisor, is a great source for determining the discomfort level of your livestock during periods of hot weather. This index can be found on the website: mesonet.org.

Establishing good management practices is vital when tending to livestock during periods of hot weather. Management options include providing shade, ventilation and air flow, clean and cool water to drink, 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 lower the animal’s core temperature. If water space is limited, provide additional portable water troughs.

Wetting is a good way to cool an animal down 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 heat stress symptoms have dissipated.

Cool water drench (administer orally) may help quickly decrease the animal’s core temperature. This method should be performed by someone who has experience in drenching an animal.

Sprinklers or hoses can provide some relief to heat-stressed animals. Water droplet size should be large to work efficiently. Misting with small droplets may only add humidity and moisture to the air. Keep in mind if livestock are not acclimated to sprinklers, they may become frightened, which will add to their stress level.

Below are some other requirements and conditions to think about when managing livestock during periods of hot water.

Water Requirements: At 90°F, water consumption can be almost twice that at 70°F. For example, on days where the temperature exceeds 80°F, cattle may need more than two gallons of water per 100 pounds of body weight. Also, water requirements vary from species to species and on metabolic and physiological needs. For instance, water needs will vary depending on the weight of the animal, physiological state (i.e. lactating), and moisture of the feeds being consumed. Water prevents dehydration and allows heat to dissipate through sweating and urination. The amount of water an animal drinks will be largely dependent on the amount of water lost through evaporation from its skin or lungs, as well as through urination. If the environmental temperature and/or physical activity increase, then it is safe to assume that water losses through evaporation and sweating will also increase.

Avoid Working or Handling Livestock: Body temperatures of livestock exposed to high daytime temperatures tend to peak in the early evening, decline during the night, reach a low point in the hours just before sunrise, and rise again slowly throughout the day. It is recommended to work/process livestock in the morning. Avoid working them in the late afternoon/early evening when their body temperatures are already high. Processing cattle can elevate their body temperatures ½ to 3½ degrees.

Confinement: Animals in confinement will usually have higher heat loads than animals grazing pasture. This is possibly due to less air movement and shade availability in a confined area. Also, there is more exposure to radiant heat associated with concrete or dark, bare soils.

Animal Weight and Body Condition: Livestock heavier in weight or having a higher body condition score (BCS) are generally more susceptible to higher heat loads than livestock lighter in weight, or with a smaller BCS.

Hide/Pelt Color: Usually, animals that have a dark color hide are more susceptible to heat stress than light colored animals. It is best to assume that all animals are susceptible to heat stress, regardless of hide color.

Transportation: If possible, avoid transporting livestock during periods of heat stress. If transportation cannot be delayed, it should be done in the evening or early morning hours when temperatures are cooler. The transportation of heat-stressed livestock to a harvest facility may have a negative effect on carcass quality, such as dark cutters in cattle, or PSE (Pale, Soft, and Exudative) in pork.

If you have questions concerning this topic or related topics, please contact the Pottawatomie County OSU Extension Center at 273-7683, stop by the office, or visit our website: http://www.oces.okstate.edu/pottawatomie/

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