• Tweet
• Printer Friendly

Managing Heat Stress in Cattle: Tips for Summer Success

Dr. Katie VanValin, Assistant Extension Professor, University of Kentucky

Temperatures and humidity are on the rise, and this combination makes cattle more susceptible to complications from heat stress. Cattle have a thermoneutral zone which is a range of temperatures and humidity where they do not need to expend extra energy to maintain their body temperature. When environmental conditions are outside of this zone than cattle are susceptible to cold or heat stress. Heat stressed cattle will exhibit increased respiration and panting to try and stay cool. Heat stress results in decreased feed intake, milk production, and average daily gains. Some cattle are more susceptible to heat stress than others, and it is important to understand that heat stress compounds other conditions such as fescue toxicosis, or respiratory disease intensifying complications from these conditions. While we have little control over weather patterns, there are several steps that can be taken to minimize the negative impacts of heat stress on the herd.

Provide adequate shade
Shade is critically important for combatting heat stress in beef cattle. In grazing animals, care should be taken to ensure cattle have access to natural shade from trees or artificial shade from shade structures. For cattle in confinement or dry lots, artificial shade sources might be a better long-term solution due to the impacts that cattle can have on tree health when provided continual access for longer periods of time. Shade structures can be portable or permanent, and both options can be effective at providing shade. Depending on the goals and needs of the operation, one option might be more practical than another. There are also plans available online for DIY construction of shade structures, as well as commercially available structures that can be purchased. Consider stability of the structure, as these structures will be susceptible to the elements, and some structures may fare better than others. A common mistake that is made with shade is not providing enough shade per animal. Beef cows need around 30-40 square feet of shade per head, with calves requiring 15-20 square feet. When looking at shade within a grazing system, proper planning can ensure that cattle have access to paddocks with ample shade during the hot and humid summer months. While it takes time to develop natural shade through tree plantings, this can be a worthwhile long-term investment to improve the utilization of the grazing system. As the saying goes, “The best time to plant a tree was 20 years ago, the second-best time is now.” For assistance with selecting tree species for pastures, reach out to your local county extension office.

Ensure clean and accessible drinking water
Cattle also need access to clean drinking water. Water intake is increased in larger cows, and in lactating cows compared to dry cows; water intake is also increased when temperatures are higher. Water requirements can reach upwards of 30 gallons per head per day for lactating cows under heat stress but may range from 15-30 gallons. Research shows that cattle drink less when water is dirty, so ensure cattle have access to clean drinking water at all times. This includes cleaning waterers and troughs regularly. Steps should be taken to prevent cattle from entering ponds, as wading and defecating in the water can increase dissolved solids and decrease consumption. It is important to monitor all water sources regularly to ensure cattle always have access, including natural water sources like ponds and streams, as dehydration can cause death quickly.

Consider forage type and fescue toxicosis
Forage type can also impact heat stress in beef cattle, especially in the fescue belt. Cattle grazing toxic endophyte-infected tall fescue, such as KY-31, and experiencing fescue toxicosis suffer from vasoconstriction, or constriction of the blood vessels, which makes it harder to dissipate heat and puts them at greater risk of heat-related complications and performance losses. One strategy to address this issue is pasture renovation—specifically, converting toxic endophyte-infected tall fescue to novel endophyte tall fescue. Novel endophyte varieties do not produce the toxic compounds found in traditional varieties but still contain the endophyte that provides persistence and stress tolerance to the plant. Pasture renovation can be costly, and not all fields are well suited for complete renovation. However, if renovation is being considered, a novel endophyte variety of tall fescue should be a top choice.

It’s important to note that the impacts of ergot alkaloids – the toxic compounds in infected fescue – can linger in cattle for weeks to months after removal from the pasture. For this reason, grazing cattle on novel endophyte tall fescue in the spring can be especially advantageous.

Interseeding legumes, such as clover, provides producers with another tool for mitigating fescue toxicosis. This has long been recommended as a tool for managing fescue toxicosis, but newer research highlights an added benefit beyond diluting consumption of toxic tall fescue. Compounds called isoflavones, especially those found in certain red clover varieties, may help alleviate the vasoconstriction caused by toxic fescue.

Producers can also consider incorporating warm-season or summer annuals into a portion of the operation. These forages can be grazed during the hottest months, allowing cool-season pastures time to rest. Take time to plan how these alternative forages can be strategically integrated into your grazing system.

Provide mineral supplementation
Mineral supplementation is important, but especially during heat stress. As cattle consume more water, urination increases, and along with that comes a loss of minerals. Cattle will crave salt, which should be provided in the form of a complete free-choice mineral supplement to cattle on pasture or can also be mixed directly into the feed for cattle in confinement. Avoid using a plane salt block to meet cattle’s desire to consume salt, because they are also losing other critical minerals such as potassium or magnesium which will not be replaced through consumption of a salt block alone. Keep a close eye on mineral feeders and ensure adequate consumption. A 50-lb bag of mineral formulated for 4 ounces per head per day should last 40 cows about 5 days, but it is important to remember that calves will also be visiting the feeder, so mineral may run out more quickly.

Adjust feeding schedule
Adjusting the feeding schedule can provide some relief for heat stressed cattle. Heat is produced as a byproduct of ruminal fermentation as cattle digest their feed. This heat production peaks about 4-6 hours after eating, so if cattle are consuming a large meal in the morning, the peak heat production would occur during the hottest part of the day. Feeding a larger portion of the daily feed in the late afternoon and evening will result in peak heat production occurring during the cooler overnight hours. Cattle are creatures of habit, so take time to slowly shift feeding towards the afternoon when hot temperatures are predicted in the extended forecast.

Modify handling practices
If possible, avoid working or transporting cattle during extreme heat events. If necessary, get cattle up early in the day before temperatures rise. This will also help to ensure the health and safety of livestock handlers as well, as people will also be at risk of developing heat-related illnesses.

Final thoughts
Summer heat events are common in the mid- and southern United States, so taking steps to improve the resiliency of the operation to heat stress will be beneficial for many years to come. Some practices like tree planting and forage renovation may take time but can have long lasting benefits. If you have any questions about managing heat stress in cattle, please reach out to your local county extension office.

Source: University of Kentucky