Summer Heat And Humidity Is Back – Monitor Your Livestock

DR. TERESA L. STECKLER

SIMPSON, ILL.
  It’s early July in southern Illinois and thus far the temperatures have not been too bad. This morning’s weather report reminded me that summer is here and temperatures are soaring. I just want to remind everyone that it is important for you and your livestock to keep cool and not work during the heat of the day.
   Searing temperatures are hard on livestock – and humans. However, 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.  It is important for producers to know what factors can contribute to heat stress.
   Cattle prefer cooler temperatures with little to no humidity. Dangerous situations can develop when temperatures approach 85 degrees 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.
   In addition to knowing those factors that can contribute to heat stress in cattle, it is important to observe your livestock frequently and take necessary precautions.
   Producers should take precautions when hot and humid weather is forecasted. Here are some tips to minimize heat stress in cattle:
   Make sure cows have access to cool, clean drinking water. A jump in outside temperatures of 10-15 degrees F can increase total water requirements by 2.5 times. The cool water will help maintain internal temperatures closer to normal. However, increased water consumption will increase urine excretion.  This results in an increased loss of certain minerals, such as sodium (a part of salt), potassium, and magnesium. Provide free choice trace mineral salt in a location where animals will consume it. Loose salt will be more readily consumed than block salt.
   Move the animals’ feeding time to late afternoon or evening. This will allow rumen fermentation to take place during the cooler night temperatures, and it will increase lung capacity for the cattle during the hotter daytime temperatures. Normal digestive processes create heat in cattle. This body heat reaches a maximum several hours after the meal is consumed. When feeding cattle in the morning of high-heat-stress days, producers may be matching peak environmental temperature with peak body temperature from digestion. Altering feed deliveries accordingly can avoid some potential additional heat from digestion.
   Remember that high quality forage produces less heat of fermentation than low quality forage. Avoid feeding excess protein during periods of heat stress.  The excess nitrogen supplied by the protein must be detoxified and prepared for excretion (via urine) which is a biochemical pathway that demands large amounts of energy.
   Ensure cattle have access to shade; trees, buildings or sunshades. Solar radiation from sunny, clear skies contributes to body temperature in cattle. Black-hided cattle in the same pens with white-hided cattle will have internal body temperatures several degrees hotter than the white-hided cattle.
   Pay attention to long- and short-term weather forecasts, have a copy of the temperature humidity index chart readily available, or just download the application (“app”). Determine the potential risk threshold and be prepared, even if the risk is several index units away. Additional solar heat, lack of air movement and heavy fat cover all can lead to disastrous effects of heat stress. The Heat Stress Forecast Maps (www.ars.usda.gov/) can provide a general guideline for expected cattle heat stress. The maps account for predicted ambient temperature, humidity, wind speed, and cloud cover.     Last year USDA’s Agricultural Research Service (ARS) has launched a new smartphone app that forecasts conditions triggering heat stress in cattle. The app is available at both Google Play and the App Store.
   Remember if you must move cattle on a hot day, take them slowly. If there are calves and you are rotating to a new pasture, cows will often travel at a speed faster than their calves. If the pasture is very far away, the calves may become overheated trying to stay with the cows. If the herd is not slowed down or made to stop, the calves may become overheated to the point of dying.
   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.
   Be prepared for heat stress. As hot weather approaches, monitor your cows frequently and the Heat Stress Forecast to determine the potential for heat stress in your cattle. ∆
   DR. TERESA L. STECKLER: Extension Specialist, Animal Systems/Beef, University of Illinois