cow drinking water

Summer months bring more than just hot temperatures to growers and ranchers.  For many, the topic of heat stress prevention becomes a hot one.  Heat stress can cause reduced breeding efficiency, milk production, feed intake, weight intake, weight gain and death in cattle.  Temperature alone is not the only way to measure heat stress; humidity and air movement are also factors.

When the humidity increases, the animal’s evapo-transpiration is reduced and the cattle cannot cool themselves.  Airflow can increase cattle comfort significantly by increasing the amount of body heat lost by convection.  Feedlot animals that are nearest to market endpoint are the most at risk for heat stress.  They are physiologically overweight and have the least amount of lung capacity relative to body weight.  Producers need to keep an eye on temperature, humidity, and wind and begin interventions well before noon.

Visible signs of heat stress include bunching, open mouth breathing, decreased activity, decreased thirst, agitation, and restlessness.  Producers also need to be on the lookout for invisible signs such as increased peripheral blood flow, and indigestibility of food.  With the heat beating down on the cattle in the mid to late summer, heat stress prevention is critical.

It’s important to make sure cows have access to cool clean drinking water.  Always check the water temperature in water troughs throughout the summer.  Keep the water cool by running lines in fields or under fences that aren’t currently being grazed and provide additional water supply for cattle in the pasture. 

It may also be time to rethink grazing strategies.  One option is to rotate cattle through fields at a more rapid rate.  Also rotate cattle before the sun rises in the morning or in the evening.  Taller grass areas tend to have a cooler surface to maintain cattle other than pastures with shorter grass.  The grass will be eaten in the evening and the digestion is consumed by mid-morning which reduces the heat produced by the animals.  Graze paddocks allow access to temporary shade or trees during the heat of the day.  This cuts down equal distribution of manure throughout the paddock but might be a suitable compromise during extreme hot weather.  Megan Brown, who earlier this year discussed Tips to Expand Your Cattle Herd, says that they move their cattle twice a year to a higher pasture which helps with both the health of their land and cattle.  The mimic natural grazing patterns and the cattle get a cooler climate, which lessens heat stress dramatically for them.  These actions not only benefit the cattle but allow for their ranching operation to use in their marketing when taking cattle to sell.

When the temperature rises, cattle start to gather in tighter groups to get away from flies which results in reduced airflow increased local humidity, elevated body temperature, and increased heat stress.  Megan Brown notes. “It is imperative that insect control is used during heat spells.  In addition to annoying cattle, insects spread disease to already immune compromised herd.”  Control the flies with the use of fly tags, sprays, and remove fly habitat including manure.  Extreme heat can make it difficult for cattle to conceive and can cause them to give birth prematurely.  With calving, Megan makes sure they provide shade, both trees and bushes, and also long and heavy grasses.  Megan adds, “We make sure to keep calves out of fields that we irrigate.  The calves will get wet from hiding in the grass, then hot from the sun, and it can cause health problems.  If I do find illness in the herd during a heatwave, I stay on top of it because it spreads so much faster throughout the herd.  If we have high 90’s or 100’s during the day, it’s a full-time job just sitting in the fields watching and listening.  If I can treat illnesses quickly, I notice fewer in the long run.”  She also adds that the breed of cattle could also help; the Bos indicus breed is more susceptible to hotter climates while the Brahman breed adapts to extreme heat and humidity. 

It’s equally important to make sure the help doesn’t get heat stressed either.  Megan says that it’s hard because you could have a lot of –“tough”- cow people that allow their egos to interfere with the care they provide to their cattle. 

Depending on the preventative method is used on your operation; the USDA provides forecast maps which are based on predictions of temperature, humidity, wind speed, and cloud cover.  Use of these maps can aid in the detection of heat stress in the cattle and hopefully stop heat stress in its tracks before it hurts your operation.

Heat in the summertime is not avoidable.  Whether its shade or water, producers can take preventative measures to keep their cattle cool and free from heat stress.  By initiating a plan ahead of time hopefully cattle will not succumb to heat stress on your operation.


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