Summer months in many U.S. regions bring higher temperatures and increased risk of heat stress in dairy and beef animals. Heat stress becomes a risk when cattle generate and absorb more heat than they are able to dissipate. Unfortunately, performance losses and clinical signs such as reduced milk production, reduced feed intake and feed efficiency, increased disease and death loss associated with heat stress contributes to significant economic losses in the dairy and beef industry every year.

Several factors come in to play when determining how an animal may become impacted by and at what environmental conditions may pose a risk for heat stress. For instance, age and production stage of the animal, management practices, nutrition, and whether or not the animal is able to effectively cool down in the evening hours determine the degree of negative effects. 

Cattle generate heat during digestion, therefore, high producing animals that eat more may be at greater risk during times when environmental conditions favor heat stress. In addition, cattle also absorb heat through solar radiation when outdoors and black hided cattle pose a greater risk of death loss during heat wave events compared to other hide colors. Heavy finished cattle with greater fat deposition have a harder time regulating heat effectively and can succumb to heat stress easier than light weight cattle.

Compared to other species, cattle don’t effectively dissipate heat and rely primarily on respiration to cool themselves. When heat load accumulates throughout the day, cattle must rely on cooler temperatures in the evening hours to effectively cool their core body temperature to a safe range.

The temperature humidity index (THI) is one measure often used to estimate the level of heat stress risk by taking environmental temperature and humidity conditions into consideration. However, since this measure doesn’t take into consideration accumulated heat load, solar radiation and wind speed the USDA’s Agriculture Research Service has implemented a Heat Stress Forecast that does calculate temperature, humidity, wind speed, solar radiation and breathing rate to more accurately access high heat stress risk environments Main : USDA ARS.

In addition to monitoring the USDA ARS Heat Stress Forecast, it is also important to be aware of the USDA ARS reported clinical signs of heat stress Recognizing Heat Stress : USDA ARS:

• Normal: no signs of heat stress
• Stage 1: elevated breathing rate, restless, spend increased time standing
• Stage 2: elevated breathing rate, slight drooling, most animals are standing and restless
• Stage 3: elevated breathing rate, excessive drooling or foaming, most animals are standing and restless, animals may group together
• Stage 4: elevated breathing rate, open mouth breathing, possible drooling, most animals standing, animals may group together
• Stage 5: elevated breathing with pushing from the flanks, open mouth breathing with tongue protruding, possible drooling, most animals standing and restless

When the Heat Stress Forecast indicates a risk level above normal in your area, be sure to observe your cattle for clinical signs associated with heat stress and determine if heat stress mitigation strategies are needed. There are several effective strategies that have been report to reduce the risk and mitigate heat stress in dairy and beef production systems. Providing adequate shade, improving air-flow/circulation throughout the pen or barn, increase water availability, implement sprinklers and consider water droplet size, and avoid certain management practices during peak heat times during the day such as handling, cattle movement, transporting, and processing cattle can improve the ability for cattle to withstand heat stress situations.

From a nutritional standpoint, there are some phytogenic feed additives (PFA) on the market that support gut functionality and reduce inflammation, thus indirectly aim to build resilience in the animal against a broad-spectrum of stress challengers, including heat and cold stress.

For more information, please contact your dsm-firmenich representative.