Cattle and Heat Stress

Cattle in general are not great at adapting to higher temperatures. The dirt or concrete surfaces of feedlots also increase radiant heat, making feedlot cattle more susceptible to the heat. Most pasture cattle are not affected by heat stress quite as easily due to the ability to seek shade, water, and air movement, but they can definitely suffer as well. When the Temperature-Humidity Index (THI) is above 80, cattle will be under heat stress. If overnight temperatures do not fall below 70˚F, they will have difficulty cooling down. Cattle accumulate heat during the day, more so if they are digesting feed. Their core temperature peaks two hours after the high air temperature of the day. After that peak, it takes cattle approximately 6 hours or more to lose that accumulated heat load. So, in essence, cattle’s core temperature does not return to normal levels a full eight hours after the maximum daily temperature. This needs to be kept in mind when processing cattle; it should only be done early in the morning, ideally before feeding time. Just because the air feels cooler in the evening to us does not mean it is safe to work cattle. This time of year, it is key to let long haul cattle sit a minimum of 24-48 hours before processing, letting them decrease both their stress and heat levels from the trip.

The USDA has created a phone app called “Heat Stress”. It consists of a map that shows the forecast for heat levels in cattle each day for the next 7 days. Feed consumption will decrease in periods of heat by as much as 20-40%, with the cattle more likely to eat towards evening. Water intake will increase significantly, with an individual animal consuming 15-20 gallons or more. Make sure to have drinking spaces of at least 2-3 linear inches per animal during the summer. Cattle are not effective at dissipating heat by sweating, they rely on respiration to cool themselves. Initial heat stress will be noticed by increased respirations, and If the heat continues the cattle will become restless and begin to drool. One of the last attempts cattle use to cool is to open mouth breathe and extend their tongue. If cattle are showing any of these signs, death is an increased risk and recovery may take a period of time. Stress levels of animals showing these signs should be kept as low as possible. Steps should be taken to lower the body temperatures of the animals. Cattle that have chronic lung damage from respiratory disease will be increasingly affected by heat stress.

There are a few methods to help your cattle cope with the heat this summer. Shade is one of the most effective prevention methods. This can be accomplished by building roofs or temporary shade structures. Effective shade should be at least 20 square feet per animal. Keep in mind that whichever method of shade is used, air movement is a critical consideration. Air movement is often forgotten when constructing feeding facilities. Buildings should have adequate airflow, such as doors or curtains that can be opened wide. Earthen mounds are very effective at exposing cattle to air movement in open lots. Cattle can also be relieved of some heat stress by water sprinkling. This can be either intermittent or continuous, but cattle need to be introduced to such methods. Keep the sprinklers away from the feed bunks and drinkers. Even if one is unable to directly spray the cattle themselves, wetting the feedlot surface will also help to decrease the ambient temperature.

However, be careful to not cause feet issues by keeping the lots too muddy. Make sure the water system has enough pressure and capacity to keep the drinkers full when the sprinklers are operational. Adding electrolytes to feed and water can be helpful, much like Gatorade in people. There are also some other products that cause vasodilation of blood vessels, allowing excess body heat to be more easily dissipated. Ask your Spencer Ag Center field marketer or call the office to find out more on these products.

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