Managing Heat Stress and Fly Control in Young Calves

Heins Family Farms in Higginsville, MO ( Wyatt Bechtel )

When the summer months can be summarized with 2 words, rain and heat, there are many complications that can arise on farms, particularly with young calves. Two of the main issues affecting health and comfort are heat stress and fly control. Management practices that can be implemented to reduce the effects of both of these problems should be explored and adopted into practice. By keeping calves cool and comfortable, we can minimize morbidity and mortality rates, economic losses, as well as time and labor spent treating sick calves. Although this is a challenging time of the year, adjusting some management strategies can provide some relief for you as well as your calves.

Heat stress in dairy calves is a topic that should be addressed on any dairy farm. When the summer months turn up the heat, most producers worry about keeping the milking herd cool. However, heat stress can be very detrimental in young calves as well by causing dehydration, weakened immune systems (due to decreased feed intake), and overall poor health. There are many options, including ventilation, increased air flow to hutches, keeping bedding dry, shade cloth, and much more that can be managed to try to keep young stock cool.

If calves are housed in individual hutches, try placing a block 6 to 8 inches high under the back of the hutch to allow more air flow into the hutch. Dr. Ted Friend, a retired Texas A&M AgriLife Research scientist and professor in the department of animal science, has done extensive research in reducing heat stress in plastic calf hutches. Dr. Friend has performed studies covering calf hutches with reflective materials to deflect some of the sun’s radiation. Some of the results using reflective hutch covers included decreased temperatures inside the hutch, lower respiration rates, less treatment rates, and improved average daily gains (Tucker, 2016). Hutches and other non-permanent condos can be oriented to catch summer breezes, while avoiding direct sunlight into the hutches during the hot afternoon hours. Enclosed calf barns can be renovated with shade cloth, temperature regulated curtains, fans, or pressure tube ventilation systems. Increased ventilation in any of these housing types can also be beneficial for helping to control the flies that gather on the calves and their environment. The area surrounding calf housing should be dry, free of tall grass and weeds, and adequately spaced apart. For individual calf hutches, ideally there should be one hutch width between hutches for good airflow and to decrease nose-to-nose contact.

Bedding is also a key player in both heat stress and fly control. Ensuring that a calf’s bedding is dry helps to decrease the incidence of flies gathering in the damp conditions and laying their eggs. Dry bedding reduces the amount of ammonia the calf is breathing and helps to keep the calf’s coat clean and dry, also eliminating a favorite spot for flies to rest. While straw is a favorable bedding for winter months, sawdust is more beneficial in the summer as it is less effective at insulating the calf. However, regardless of the preferred bedding, ensuring that there is adequate, dry bedding is what makes the difference. To get a good idea of how wet the bedding is, use the knee test to see how you are doing. Enter the calf’s pen and drop to one or both knees. If your knees are damp or wet, the bedding needs replaced or replenished.

Another important must have is water, water, water. All calves should have access to fresh, clean drinking water at all times, both winter and summer months. However, as the summer heat rises, a calf must have access to water in order to prevent dehydration and to cool body temperatures to a manageable level. In addition to cooling body temperatures down, water availability encourages feed intake and is an essential component to rumen development. It is important to provide a barrier or some degree of separation between food and water buckets. When calves can play between the two buckets, they will have a greater tendency to make their bedding as well as their feed wet, creating another favorable spot for flies to congregate.

Even when management practices are at their best, fly populations can still be a nuisance for any farm. Ensuring that we are keeping the environment around our calves as clean and dry as possible is a great step in control; however, there are insecticides and other additives that can be used to cut down on fly numbers. There are options available to spray insecticides throughout calf housing to decrease populations. These methods generally have to be repeated on a regular basis. There are effective additives that can be incorporated into dry feeds as well as milk replacers that harmlessly pass through the digestive system and are excreted into the manure. When eggs are laid in the manure, the life cycle of the fly is interrupted, preventing the larvae from maturing into an adult fly.

One of the biggest challenges for farmers is to compete with Mother Nature. When the seasons bring less than favorable conditions, there are management practices that can be implemented to try to lessen the severity of these conditions. When summer months bring an excess amount of rain and heat, keeping your calves dry and comfortable will provide both immediate and long term results that will have been well worth the extra effort.