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It’s Always Important To Observe Your Cattle Throughout The Summer
DR. TERESA L. STECKLER
SIMPSON, ILL.
While the corn is up and growing well, the recent rains have made planting soybeans and harvesting hay nearly impossible. The cool wet conditions further delayed hay production. However, this is the Midwest, the hot and humid weather will return like clockwork.
With the increasing temperatures and humidity and push to plant beans and harvest hay, it is important not to forget your livestock and the effects of heat stress. The combination of high temperatures and humidity can create an especially dangerous situation for livestock. High temperatures and humidity can negatively impact breeding efficiency, milk production, feed intake, weight gains, and sometimes cause death.
Animals lose body heat by radiation, conduction, convection and evaporation. As the environmental temperature continues to increase, the cow must rely more on evaporative cooling (sweating and panting) to lose body heat. But as the environmental temperature increases, the temperature difference between the cow's body and the surroundings is reduced, reducing the amount of body heat that can be lost.
Cattle prefer cooler temperatures with little to no humidity. Dangerous situations can develop when temperatures approach 85 F with high humidity and as temperatures soar so does the potential danger to livestock.
Numerous factors contribute cattle’s susceptibility to heat stress. Basically, these factors can be categorized as environmental or animal-related. Environmental factors include ambient temperature, solar radiation, humidity, wind speed, soil moisture, and overnight temperatures. Animal-related factors include origin of the cattle, acclimation to the environment, age, health, hair coat, nutrition, and genetics. Genetics influences hair color and temperament.
There are several signs of heat stress in cattle and it is important to recognize these as soon as possible. Signs of heat stress include bunching (in the shade if it’s available), slobbering, high respiratory rates (panting), open mouth breathing, lack of coordination, and trembling. If you see these signs, assume the cattle have high heat loads, and minimize the stress immediately, but handle the animals gently to avoid increasing their stress even more.
All these factors should be taken into consideration when determining whether your cattle are susceptible to heat stress. While you cannot control the weather, the Heat Stress Forecast Maps can provide a general guideline for expected cattle heat stress (www.ars.usda.gov/). The maps account for predicted ambient temperature, humidity, wind speed, and cloud cover.
Because of the importance of water to body function and the difficulty in estimating requirements, cattle in all circumstances should have free access to all the quality water they will consume. Numerous factors influence the amount of water required by cattle. Water consumption varies considerably, depending on the temperature and stage of production. Water consumption is influenced by other factors, such as moisture and protein level of the feed, salt intake, relative humidity and the breed of cattle. In areas with high humidity, animals require somewhat less water because of lower losses to evaporation.
Increased water consumption will increase excretion of urine. This will also increase the loss of certain minerals, such as sodium (a part of salt), potassium, and magnesium. Free choice trace mineral salt should be provided in a location that the animals will consume it. Loose salt will be more readily consumed than block salt.
Ensure that all livestock have access to shade; trees, buildings or sunshades. If the shade is concentrated in one area newborn calves may be stepped on or develop navel ill due to the accumulation of mud. Check the calves daily and dip all navels of newborns. If possible move the herd to a pasture that provides plenty of shade.
Depending on the distance, moving cattle from one pasture to another will increase their body temperature. Try to move the cattle early in the morning or late evening to minimize heat stress. Also calves can become overheated, so keep a close eye on them.
Also, do not forget about the bull and the effects of heat stress on him. He will have lower libido, lower sperm production and decreased semen quality. Keep in mind that heat stress can impact semen quality for up to eight weeks.
Remember if you are hot while working, so are your cows and calves. Heat stress can greatly impact cattle producers through decreased milk production and subsequent calf growth, decreased reproductive performance in cows and bulls, and decreased stocker and feeder performance. To minimize the impact of heat stress, livestock producers need to be flexible when managing their livestock during these dangerous periods. ∆
DR. TERESA L. STECKLER: Extension Specialist, Animal Systems/Beef, University of Illinois
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