Housing technology has advanced in the poultry industry above all other animal production industries. Cooling systems like evaporative cooling and tunnel ventilation, as well as insulated roofs and walls, help mitigate the negative consequences of heat stress in poultry operations.
While advanced housing technology helps birds survive in higher temperatures (higher than 92 F, 60% relative humidity), in regions like the southern United States, temperatures can reach over 100 F. When this happens, the heat can overpower the cooling systems and leave your flock susceptible to heat stress.
Feeding performance trace minerals, combined with the use of appropriate housing technology, can help mitigate heat stress in your poultry flock and help them reach their market weight on time.
The productive life for broilers is 35 to 57 days and a little less than two years for laying hens. As a result, there is a much smaller margin for error in heat stress management especially for broilers because there is less time to recover. For layers, heat stress can have a lasting effect that can impact egg quality for days even after temperatures have returned to normal.
When a bird’s body temperature increases, blood flow is diverted from the visceral blood vessels of the digestive tract to the skin to increase heat dissipation. This reduces the amount of oxygen (hypoxia) and nutrients available to the enterocytes (single-layer epithelial cells) lining the gastrointestinal tract. As a result, the tight junctions weaken and allow pathogens and their toxins to transfer into the bloodstream, ultimately leading to leaky gut.
Chickens pant in order to increase evaporative cooling. Evaporation of one gram of water is capable of dissipating 540 calories of maintenance energy, which can ultimately lead to the development of lower-quality eggs in laying hens and a lower feeding efficiency and growth rate in broilers.
There are two main cooling systems that are popular in poultry operations. The most popular is tunnel ventilation. With a tunnel ventilation system, large fans are installed on one end of the house and create air movement by pulling air through the house and carrying the hot air out.
An evaporative cooling system uses the heat in the air to change water from liquid to gas. This releases energy and takes the heat out of the birds and of the house environment.
Evaporative cooling systems can include:
In high humidity conditions (higher than 80%), evaporative heat loss and evaporative cooling systems become inefficient. In these conditions, convective cooling (air flow) is the only alternative to help birds dissipate heat. Proper maintenance is important for housing cooling systems to be efficient. Adequate sealing, level of airflow and good conditions of thermal insulation materials in roofs and walls must be maintained.
During extremely hot weather, poultry producers should also consider implementing a summer nutrition and feeding program.
Birds will naturally eat less during extreme heat events, so nutritionists and poultry producers should feed a more nutrient-dense diet to compensate for the reduction in feed intake. This includes increasing the fat-to-carbohydrate ratio since fat is a more efficient energy source. After chickens eat, their body temperature increases and causes discomfort. Providing more fat uses less metabolic energy, reducing this body temperature increase.
Formulating diets for digestible amino acids also becomes critical in hot weather. Diets are concentrated, and protein is reduced to marginal levels to reduce the heat increment. To compensate for this reduction and maintain a constant intake of these nutrients, amino acid ratios have to be in good balance. Producers should also make sure they have a good electrolyte balance in their poultry nutrition and feeding program. When birds pant, their blood tends to become alkaline, resulting in an eventual loss of sodium. Electrolytes provide a good balance of sodium, chloride and potassium, and helps to keep the buffer capacity in the blood. It is recommended that producers supplement 242–300 milliequivalents of electrolytes per kilogram of feed. Additionally, producers should increase their supplementation of vitamins C and E.
Another consideration in extreme situations is restricting feed intake during the hottest times of day. Instead, producers should provide light after the sun goes down, when birds are more comfortable, to allow them to eat at that time.
Producers should increase their trace mineral supplementation with performance trace minerals, especially zinc, manganese and selenium.
Zinc strengthens the bonds between the epithelial cells in the gastrointestinal tract, helping to maintain the tight junctions during a challenge and decreasing the occurrence of leaky gut and related intestinal inflammation.
Oxidative stress occurs when free radicals and antioxidants are out of balance. Zinc, copper, manganese and selenium work as antioxidants by removing free radicals and protecting cell membranes from oxidative damage. Requirements for these minerals increase during stress events.
During hot summer weather, it is recommended that nutritionists and poultry producers supplement 40 ppm of zinc from Availa®Zn or 40/40 ppm of zinc and manganese from Availa®Z/M on top of their regular year-round supplementation levels. Supplementation levels of selenium from Availa®Se* should increase by 0.2 ppm, and chromium from Availa®Cr* should be incorporated at 0.4 ppm.
Housing technology in the poultry industry can help mitigate the negative impacts of heat stress during the hot summer months. In regions where the heat can overpower your cooling systems, increasing your supplementation levels of performance trace minerals can keep birds comfortable and productive.
*Note: Not all products available in all markets