As the mercury rises, heat stress emerges as a growing challenge for poultry health and a profit stealer for poultry farmers. This article delves into the heart of heat stress, revealing its impacts on laying hens in particular. Among the mitigation strategies necessary to shield birds from the effects of the heat, nutritional adaptation is key and easy to implement. Follow our guide and discover how dietary tweaks can turn the tide against the heat, safeguarding the well-being and efficiency of poultry farms.

An invisible threat

Global climate change poses a great threat to poultry production. Heat stress stands as one of the primary stress factors impacting poultry productivity in regions with hot climates, resulting in significant economic losses for the poultry industry. Heat stress commences when the surrounding temperature exceeds the thermoneutral zone of the chicken (Generally between 18–25°C). Within this temperature range, sensible heat loss is adequate to maintain the bird’s normal body temperature of 41°C.

Heat stress can significantly impact a flock’s productivity. While temperatures exceeding 33°C are associated with evident high mortality rates and substantial production losses, at milder temperatures, heat stress is frequently underestimated as a factor contributing to suboptimal growth or subtle declines in egg production and shell quality.

When temperatures surpass the thermoneutral zone, birds must allocate energy to sustain their normal body temperature and metabolic functions. This allocation of energy away from growth and egg production leads to a decline in overall performance.

How does heat stress affect laying hens?

When exposed to 30°C, hens exhibit reduced feed intake, leading to smaller egg sizes and ultimately decreased egg production.
As the temperature rises from 30 to 38°C, there is a likelihood of deteriorating shell quality. Beyond 38°C, birds can only dissipate body heat through intense panting, leading to respiratory alkalosis. This physiological response is characterized by elevated blood pH levels and a decrease in blood CO2 concentration. This disrupts the acid-base balance and leads to a reduction in blood calcium and bicarbonate levels, essential for the production of strong eggshells.
Beyond 41°C, the risk of mortality increases significantly.

The cooling power of nutrition

Several significant studies have indicated the potential of dietary adjustments in mitigating the adverse effects of heat stress on poultry productivity. Integrating essential dietary modifications alongside proper management practices can help maintain optimal health and performance in poultry flocks during periods of elevated ambient temperature.

When formulating the diet for hot weather conditions, there are several things to consider:

• Including oil in the diet has long proved to be beneficiary in hot climates. The digestion of fats generates less heat compared to the digestion of carbohydrates and proteins. Elevating the ratio of energy derived from easily digestible fats, rather than starches or proteins, decreases the body’s heat production during digestion. This phenomenon, known as heat increment, is minimized when digesting dietary fats.
• Increase use of synthetic amino acid. Under conditions of heat stress, chickens experience a decrease in feed intake, leading also to reduced protein consumption. The protein content in poultry diets during heat stress needs careful consideration. Set digestible amino acid targets instead of imposing a high minimum crude protein level in the formulation. The use of synthetic amino acids allows for a reduction in crude protein content in the diet without compromising amino acid levels. Supplementing low-crude protein diets with essential amino acids has emerged as a valuable nutritional tactic to mitigate the adverse effects of heat stress and reduce the environmental footprint of poultry production.
• Increase phosphorus. The demand for phosphorus rises during heat stress, increases up to 5% are deemed suitable under such conditions.
• Using electrolytes in drinking water for up to three days in heat stress periods is beneficial as heat stress causes increased loss of several minerals including potassium, sodium, phosphorus, magnesium and zinc.
• Sodium bicarbonate supplementation. Including sodium bicarbonate in the feed or using carbonated water is particularly beneficial for hens involved in egg production. Panting and the release of carbon dioxide can alter the acid-base balance in heat stress periods, affecting the availability of bicarbonate crucial for eggshell formation. Therefore, sodium bicarbonate can aid in mitigating these alterations.
• Supply antioxidants. With decreased feed intake, there’s a corresponding reduction in the intake of vitamins and trace minerals. Several of these micronutrients, especially B vitamins and antioxidants, could prove advantageous for birds under heat stress conditions. Supplementing drinking water with vitamins (A, D, E and B complex) can be effective at tackling heat stress. In particular, Ascorbic Acid (Vitamin C), a water-soluble antioxidant, protects cells from oxidative damage and mitigates the adverse effects of heat stress. Vitamin C can be added to feed or water, supplementing Vitamin C at approximately 200-250mg/kg of feed enhances production, nutrient digestibility, immune responses, and antioxidant capacity. Research has shown that supplementing a combination of vitamins C and E yields greater benefits compared to providing them individually, thanks to their synergistic effects and antioxidant properties in mitigating heat stress.

For more information about poultry feed formulation under heat stress and adapted vitamin and minerals solutions, contact us.