Beat heat stress

This won’t come as a news flash: it is important to have enough water and shade for cattle. Cattle can tolerate summer temperatures and remain productive when properly managed and allowed access to adequate fresh water and shade.

But what you might not realize is that cattle are most productive when temperatures are between 41ºF and 77ºF. Temperatures above that put cattle at a greater chance for heat stress: decreased reproductive performance, decreased calf performance, lower milk production, and the rest.

There are many environmental factors that affect cattle and their potential for heat stress, including relative humidity, wind speed, solar radiation, ground cover, access to water, diet, shade and temperature. Animal characteristics can also contribute to heat stress, including color, breed, health, adaptation, hair length and disposition.

Heat stress occurs when these factors and ambient temperature cause an animal’s heat load to exceed its ability to dissipate that heat.

Available water and adequate shade are effective at reducing the effects of heat stress. The amount of shade required is 30 to 40 square feet for mature cattle, 20 to 25 square feet for feeder cattle and 15 to 20 square feet for stockers. Heat stress is compounded by animals crowding together, which happens when shade is limited. If natural shade is inadequate, construct permanent or portable shade structures.

Permanent structures are more suitable for feeding pens and but are frequently placed in pastures as well. Portable structures are more expensive to construct but can be moved with the cattle. The advantages to portable structures include: more uniform grazing, less pasture damage in the shaded areas and better manure distribution. Locate shade structures in areas to take advantage of prevailing winds during the summer. Select areas with minimal slope to prevent erosion that can result from concentrated animal traffic.

All shade structures should allow adequate airflow. Permanent structures will require manure removal in some situations. Inexpensive UV-resistant shade cloths that block at least 80-90 percent of light, or two offset layers of snow fence provide adequate shade and allow for proper airflow. Solid coverings are more expensive and last longer but are more susceptible to wind damage. If a solid cover is used, then the structure will need to be taller.

You can affect heat stress through feeding, too. One way is to reduce forage to minimum effective fiber levels. Practically speaking, this is a difficult task, in that many beef cattle are eating principally forage diets. That said, the tactics would be to feed the best forage available and use additives that help alleviate heat stress. From our perspective, the product of choice is MFA Ricochet FesQ Max products.

Additionally, feeding a yeast culture helps for heat. The feeding rate depends on the product but ranges from 10 grams per head per day to 10 ounces per head per day. All MFA Gold Minerals and dairy feeds have yeast cultures, as do Trendsetter, Cattle Charge and Full Throttle. The same goes for Aspergillus oryzae, which is usually fed at 3 grams per head per day. Some products/brands suggest as high as 15 grams per day.

Potassium is a consideration as well. Usually, beef animals on forage diets are high in potassium, but when more concentrate is fed, potassium content declines. Thus, under heat stress, you can add potassium to equal 1.5 percent of the entire diet intake. The source that works the best is potassium carbonate, but since this is a costly mineral, most of us use potassium chloride.

Feeding fat increases energy, reduces package size, reduces fiber content and load without increasing acidosis risk. For beef, I feed up to a pound of fat. For dairy animals, I feed a pound of fat as a vegetable (roasted soybeans), 1 pound as animal (Taltec) and 1 pound as a “bypass” fat (megalac etc.). But that is where I stop—overfeeding fat, especially vegetable fat, will reduce fiber digestion and intake, which is exactly what we don’t want for milk production in heat-stressed cows.

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