While some areas of the country are still getting over the long-suffered winter weather conditions, other parts of the U.S. have warmed up to typical mid-spring temperatures. As I write this from my home in Virginia, we are expecting highs in the 80s for most of this week — which means that livestock here and in other parts of the South are already experiencing some form of heat stress. Fortunately, at this time of year, temperatures are not yet extreme, and, at night, they typically decrease until they fall below the heat stress threshold. We know, however, that higher sustained temperatures and humidity are right around the corner, so we cannot afford to delay making preparations that will help our livestock deal with these extremes.

All livestock have what is called a “thermoneutral zone,” defined as the temperature range in which no energy is expended to maintain homeostasis, or a constant body temperature. Just as with people, there will be some variation from animal to animal, but we know that, when the temperature and humidity go above this thermoneutral zone, the animal will be required to expend energy in order to stay cool. The “Temperature Humidity Index” (THI) chart below is used as a guide by many in the cattle industry to help manage cattle as the THI approaches either danger or emergency levels, which could severely impact animal health.

(from Noble Research Institute, 1999)

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RELATED: Regulating body temperature during heat (or cold) stress
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One sign of heat stress is an elevated respiration rate, as cattle can expel some heat from their bodies through their mouths. When severe panting occurs, cattle can lose the important sodium bicarbonate produced naturally during chewing. Sodium bicarbonate works to keep rumen pH at a desirable level, so decreased levels of sodium bicarbonate can lead to rumen acidosis, reduced feed intake and reduced performance. Under heat stress, core body temperatures can increase, and — again, much like humans — livestock will reduce their overall feed intake, once again impacting production through reduced weight gain or weight loss and decreased milk production. Studies also indicate that early embryonic loss can increase in cows under heat stress, so planning one’s breeding period for cooler times of the year could improve conception rates.

Five management tips for reducing heat stress

1. First and foremost, always provide a source of cool, clean water for your livestock. Research has shown that, at increased ambient temperatures, animals consume cooler water at a significantly higher rate than warm water. Proper water management, such as keeping water troughs or streams clean, is extremely important to avoid reduced intake.  
   
   
2. Providing a source of shade in pastures where no natural shade is available can be very beneficial. Portable shade barriers can be moved and will also reduce the muddy and torn-up areas in the field. Many studies have shown increased feed intake, conception rates, milk production and growth when shade is provided to livestock.
   
   
3. When cattle are confined, such as in dairy herds or show barns, producers often use a combination of fans and misters. Fans alone are not very effective for cooling, as cattle do not sweat enough for the air moving over them to provide adequate evaporative cooling, as illustrated in the chart below.
   
   Management strategies to reduce heat stress, prevent mastitis and improve milk quality in dairy cows and heifers, Extension Bulletin 1426, U. of GA
   
   
   
4. A good fly control program can reduce the activity level of livestock, since they create heat and expend a great deal of energy dealing with flies. As a nuisance pest, flies increase stress through biting and eye irritation, causing animals to swish their tails and shake their heads. There is also a natural inclination to congregate closely, reducing the movement of air and its cooling effect.
   
   
5. Ensure that the diet is nutritionally balanced. Forcing the body to expel excess nutrients increases energy expenditures and results in a buildup of internal heat. For example, we all know that protein is essential for many daily functions, but feeding too much protein beyond the required levels results in the body working harder to get rid of the excess nitrogen supplied by the protein.

Controlling the fiber content of the diet — by reducing fiber in favor of energy sources that are easier to digest, such as grain — can also reduce the internal heat load. Ruminants typically do this on their own, sorting the more fibrous feeds from the grains in the TMR. A common misconception is that grains like corn, wheat, barley and oats make cattle warmer, since they are often referred to as “hot” feeds. In reality, grains are more easily digested than forages, so the “heat of digestion” of grains is lower than that of forages, because digesting forages requires a higher expenditure of microbial energy. As a youngster growing up on a dairy farm in western New York, I learned that feeding more hay in cold weather is a scientifically sound practice for helping cows stay warm.

The CRYSTALYX^® difference

Consider including CRYSTALYX self-fed nutritional options for multiple species to help offset the challenges of heat stress. The high-molasses formulas are extremely palatable, providing sugars and proteins that enhance the digestibility of forages at a time when forage intake may be decreasing in order to reduce the heat load. All CRYSTALYX formulas contain the vital vitamins and minerals that, again, your animals may need more of due to lower consumption during heat stress or that are lost through drooled saliva, which negatively affects production.

In cattle, the action of licking helps induce the natural production of sodium bicarbonate, which reduces the incidence of low rumen pH. Buffer-lyx^® is a patented buffered lick tub for dairy cattle that — in addition to enhancing the natural production of sodium bicarbonate — provides supplemental buffers to help alleviate subacute ruminal acidosis (SARA). Fly control products with Rabon^® (such as Rolyx^® Pro-Mag and Rolyx^® Max for beef or dairy cattle and horses), Altosid^® IGR (IGR PRO™ and IGR MAX™ for cattle) or Clarifly^® (Mineral-lyx^® for cattle and horses, or Stable-lyx^® for horses) can help reduce fly irritation. 

For additional information on CRYSTALYX products that can help during times of heat stress, please contact your local dealer.