Mitigating heat stress is crucial during the summer, not only for humans but also for cattle. A proactive approach can help maintain cattle comfort before a period of high heat. Understanding the signs of heat stress, effective strategies to combat it, and maintaining optimal conditions to keep cattle cool are critical to beating the heat throughout warmer months. Monitoring heat stress opportunities in cattle is relatively easy and is the same as monitoring heat stress for humans. The heat index is one of the simplest and most easily found metrics to predict when chances for heat stress-related events are most likely.
What Makes Cattle Susceptible
Heat stress in cattle arises when their heat production and absorption surpass their capacity to dissipate heat efficiently through respiration, sweating and exposure to air currents. Compared to other species, cows do not sweat effectively and rely on respiration to cool themselves, making them more sensitive to extreme conditions. Cows begin to experience heat stress at a much lower temperature than humans, with potential for mild stress starting at 72°F and 50% humidity.
It is important to realize that while hot summer days and nights are of most concern, cattle can experience heat stress at any time of year. While typically short lived, a warm day in February or March can be stressful for cattle not acclimated to that kind of heat. Additionally, black-hided cattle will have higher incidence of heat stress than red- or white-hided cattle. Bos Indicus cattle (such as Brahman) have a higher heat tolerance than Bos Taurus cattle (such as Angus, Hereford or Simmental, English or Continental breeds).
Heat Stress Signs
Heat stress indicators can be overlooked in cattle, so it’s vital to know the signs to ensure heat stress can be addressed quickly. Watch if cattle are becoming restless or spend increased time standing. Also, be sure to pay attention to rumination, cows’ respiration rate (normal respiratory rates for an adult cow can range from 40 to 60 breaths per minute), when cows are eating, how many cows are eating, and variation in feed consumption over the day. If cows deviate from normal behaviors, especially in comparison to their behavior during cooler or more ideal temperatures, it could be a sign of distress.
Cattle experiencing heat stress will have markedly reduced feed intake (as much as half of what they would eat without heat stress), which can not only result in lower ADG, but will result in lower conception rates in breeding cattle. Often overlooked, but critically important, is the heat stress bulls experience during the breeding season. Not only can heat stressed bulls experience decreased semen quality, but a heat stressed bull can have greatly reduced libido that can result in open cows.
Moreover, heat stress can affect a cow’s gastrointestinal tract due to the animal being exceptionally sensitive to hypoxia and nutrition depletion. This could lead to a “leaky gut,” which increases intestinal cell permeability and could lead to a more severe symptom: sepsis.
Heat Stress Mitigation
Management strategies should be of the utmost priority during summer months, and access to shade and clean water should be readily available. One cow can need anywhere from 100 liters of water per day to, sometimes, up to 160 liters (25 to 50 gallons) per day during higher temperatures. Ensuring
cattle also have access to free-flowing air is also critical. Wind breaks that are of great benefit to cattle in the winter can cause stagnant breezes in the summer and exacerbate heat stress. Using fly control measures will help cattle disperse and maximize air flow, while additionally increasing cattle comfort by not having to constantly battle flies and insects.
Additionally, feed additives can be used to minimize risk of heat stress. Understanding how the body prioritizes nutrients the animal needs is the first step in leveraging nutrition to mitigate stress. During periods of stress, the allocation of nutrients undergoes a natural shift away from purposes such as animal growth or reproduction, aiming to mitigate the adverse effects. As the body prioritizes the immediate requirement of assisting the animal in coping with stress, the availability of nutrients can become restricted, leading to subsequent effects on growth performance or fetal growth.
Scientific advancements in animal nutrition have identified ingredients that aid cows in coping with the effects of high temperatures. Research trials have demonstrated the beneficial effects of specific plant extracts fed in the right ratios and amounts in mitigating the cow’s responses to the effects of stress. ADM’s unique blend of plant extracts has shown in research trials to improve ADG and feed efficiency during the hot summer months by maintaining intakes seen in months prior to heat stress. Additionally, cattle in these trials spent less time crowding the water and behaved in a much more “normal” manner than the cattle not receiving the blend of plant extracts. These beneficial responses have been documented in feedlot cattle with or without the presence of an ionophore.
It is important to note the feed additive tested in these internal ADM trials is a blend of three extracts and not any singular extract. Additionally, the technology of getting the extracts into the animal in an inert manner is very important due to potential negative palatability concerns without the proper coating on the product. In other words, not all products in this class are created or delivered equally.
During times of moderate to extreme heat stress, cattle producers must stay vigilant in providing the most comfortable environment possible for the animal’s well-being. Whether cows, calves, yearlings or feedlot cattle, comfortable animals are more productive than stressed animals. Fortunately, exceptional management, functional feed additives and other nutritional solutions are available to help ranchers optimize animal performance during challenging conditions.
