Heat stress can contribute to many production challenges and can be costly for poultry producers. During heat stress, birds eat less than they should to reduce their body temperature, leading to a reduction in metabolizable energy consumption. The detrimental effects of heat stress on broilers and laying hens range from reduced growth and egg production to decreased meat and egg quality and wellness.
The productive life for poultry is much shorter than other animals: about 47 days for broiler chickens and as little as one year for layer hens. For this reason, there is a much smaller margin for error in heat stress management than in larger animals because there is less time to recover.
Production challenges from heat stress can be seen during a bird’s first week of life because young chicks do not fully develop the ability to regulate their body temperature. The digestive tract shows signs of weakness and accelerates the transit of food, resulting in a considerable reduction in digestion and absorption of nutrients.
How Do Chickens Dissipate Body Heat?
Unlike other animals, birds do not have sweat glands to help with heat loss. There are four main ways in which birds remove excess body heat: radiation, conduction, convection and, when those three ways aren’t enough, by evaporation.
Radiation is when the bird transfers heat from the surface of its skin, through the air, to another object, including other birds. This is where high flock densities become a challenge during the hot summer months.
Birds dissipate body heat by conduction by transferring heat to cooler objects with which they come in contact, such as feeders, slats or water from sprinklers. That, too, can become a challenge since sprinklers increase humidity, increasing the thermal sensation from the heat.
Convection occurs when wind contacts the skin and carries the heat away. Chickens often raise their wings to expose lightly feathered skin and increase the surface area for body heat dissipation.
When a bird’s body temperature reaches 106° F (41° C), the efficiency of radiation, conduction and convection is reduced, and evaporation of water from the respiratory tract from panting becomes their main mechanism of heat loss. Evaporation of one gram of water is capable of dissipating 540 calories of maintenance energy. In addition, the birds’ nasal cavities work by filtering dust and bacteria from the air entering the respiratory tract. Using the respiratory system for evaporative heat loss can lead to an increased incidence of second bacterial infections. Eventually, without relief from the heat, birds will often tire from heat exhaustion.
Heat Stress in Poultry Leads to Inflammation
When feed intake is reduced during heat stress, birds will also have reduced blood flow in the gastrointestinal tract, which leads to a reduction in the amount of oxygen (hypoxia) and oxidative stress in the intestinal tissues. As a result, the tight junctions that hold those epithelial cells (enterocytes) together weaken, increasing permeability and allowing pathogens and their toxins to enter the gastrointestinal tract. This is a condition called leaky gut and can result in chronic inflammation. This inflammation will trigger the immune system to consume significant levels of nutrients to deal with the inflammation, reducing the amount of nutrients available for muscle growth or egg production.
Heat Stress Impacts Eggshell Formation
When chickens pant, they lose CO2 through respiration, which causes the pH of the blood to become more alkaline and reduces the amount of ionized calcium in the blood, which can lead to bone problems.
For laying hens, since they require a high amount of calcium for eggshell formation, it often results in the development of thin-shelled or smaller eggs and/or a decrease in egg production. For broilers, producers will often see an additional decrease in feed intake, feeding efficiency and growth rate.
Performance Trace Mineral Nutrition for Heat Stress Management
Managing the production challenges related to heat stress in poultry production can be mitigated by adjusting your poultry nutrition program. Major changes to the diet in the summer months should always focus on reducing oxidative stress, preserving the integrity of epithelial tissues in the gastrointestinal tract and increasing heat tolerance.
Major nutritional changes poultry producers and nutritionists should consider during the hot summer months include the following:
- Feeding a more nutrient-dense diet, to compensate for feed intake reduction
- Including performance trace minerals in the diets, to increase antioxidant capacity and thermal tolerance of bird organism.
Reducing Oxidative Stress, Increasing Thermal Tolerance
During the hot summer months, the use of performance trace minerals is crucial. The most important antioxidant systems in the animal organism depend on zinc, manganese, copper and selenium. They serve as molecule cofactors and for enzyme activation, such as the SOD (Superoxide dismutase) system and glutathione peroxidase (GPx). Oxidative stress occurs when free radicals and antioxidants are out of balance. These antioxidant systems work by removing free radicals and protecting cell membranes from oxidative stress.
Zinc also plays an essential role in the formation of structural components of tissues, molecules and epithelial cells present in the intestine. Research show that feeding zinc from Zinpro® Availa® Zn strengthens the bonds between the epithelial cells in the gastrointestinal tract, helping maintain tight junctions during a challenge and decreasing the occurrence of leaky gut related intestinal inflammation.
Chromium from Zinpro® Availa® Cr or Zinpro® MICROPLEX® can increase thermal tolerance as it helps to reduce the level of corticosterone — involved in regulation of energy, immune reactions and stress responses — in poultry. Elevated levels of corticosterone cause animals to behave in a hectic manner, expend energy and, ultimately, reduce feed intake. Lowering corticosterone levels with Zinpro Availa Cr or Zinpro MICROPLEX can help keep animals calm and keep them more willing to eat during heat stress events.
Heat stress can result in production challenges that are costly for poultry producers. Including performance trace minerals in your poultry nutrition program, you can help mitigate these challenges and make your operation more profitable.
Contact a Zinpro representative today to learn more about including Zinpro Performance Minerals®, like Zinpro Availa Cr, Zinpro MICROPLEX, Zinpro Availa Zn, Zinpro® Availa® Mn, Zinpro® Availa® Cu and Zinpro® Availa® Se into your livestock and poultry nutrition programs.
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