When we think about heat stress in cattle, the first thing that comes to mind are cattle that are in confinement, such as dairy animals. Interestingly enough, the animals that are most susceptible to heat stress are those that are in fields where shade and or air movement may be limited given that animals in confinement have some means of artificial cooling to relieve stress. Usually, those animals in confinement are in a controlled situation in regards to air movement, usually with fans or misters to make them more comfortable.
It is important to remember that cattle become uncomfortable at temperatures 20 degrees less than the temperature where humans become uncomfortable. This means that if you are uncomfortable at 80 degrees, and feel hot at 90 degrees, cattle may already be in the danger zone at these temperatures. Cattle that are heavier (in excess of 1,000 lbs.), and dark hided cattle, along with cattle that may be stressed due to disease or transportation will be more susceptible to heat related stresses than any others. Another complicating factor in heat stress is that of humidity. As humidity increases, it becomes increasingly difficult for cattle to dissipate body heat, much as in humans.
Producers should realize that it is not possible to control the weather and some instances will occur that are beyond their control. Not all stresses can be eliminated under usual production practices, but measures should be taken to make cattle more comfortable where possible and practical. Some of those measures are listed below:
Shade: Where possible, provide either natural or artificial shade for cattle. Altering fencing or opening up a new pasture for animals will sometimes allow cattle access to areas where air movement and shade are more available. Portable shades can be utilized as well especially when placed on higher ground to allow air movement to help cool the animals. Shade can be built or be as simple as parking machinery or trailers in the field to provide shade in the afternoon.
Water: Assure that your animals have a water source that is clean to insure adequate water intake. While water temperature is not important up to about 90 degrees, keep in mind that a lot of black or dark colored tanks can increase water temperature to more than 100 degrees. The same is true for black plastic pipe supplying water to animals in the field. Therefore, it is wise to place water tanks in shady areas near where the animals will be loafing during the hot part of the day or use lighter colored tanks to reduce water temperature. Intake is extremely important as cattle can drink 1% of their body weight per hour when stressed by temperature.
Reduce Management Stress: Try not to do any more management related practices such as health programs, castration, weaning, etc. when temperature result in dangerous THI values. If necessary to treat animals or move them through a handling facility, try to do these practices at night when it is cool or very early in the morning to reduce stress. Cattle should not spend more than 30 minutes in the facility when the THI value is above 79. This would also apply to any necessary movement of cattle from field to field.
Plan Transportation: When transporting cattle during hot weather, plan to haul cattle during the cooler parts of the day such as later at night or early in the morning while allowing ample time for the cattle to become adjusted and find shade once they reach their destination. Don’t crowd cattle in trailers during hot weather, allowing extra space to reduce stress.
Know the Signs of Heat Stress: When cattle are extremely stressed, they will become lethargic and may be seen panting for breath. Some cattle will breathe with their mouth open and be seen with excess saliva hanging from the mouth. When these signs are noticed, producers should take every effort practical to cool the animals immediately. This might include spraying with water, moving the animal to an area where air movement is better, moving the animal under a fan, or providing artificial shade if the animal is non-ambulatory. Heat stress is a real concern for producers and can greatly decrease profitability. It is important to remember however that there are usual and customary production practices that are commonly accepted in beef cattle management. While producers should provide certain measures of comfort, there will be limits as to what is practical and appropriate to provide.