Heat stress is one of the main challenges faced in egg production, significantly affecting the performance and health of laying poultry. When exposed to high temperatures, poultry undergo a series of physiological changes that compromise their well-being and productivity.

One of the direct consequences of heat stress is a reduction in feed consumption, which leads to a lower intake of essential nutrients for maintaining health and egg production. As a result, one can notice a drop in both the quantity and quality of the eggs produced, with smaller eggs and thinner shells.

In addition, heat stress causes changes in the electrolyte and acid-base balance of the poultry, which can lead to increased mortality in the flock. The immunosuppression caused by stress also makes poultry more susceptible to disease, further compromising productivity.

Physiologically, poultry do not have sweat glands, which makes it difficult for them to dissipate heat. To try to compensate, they increase their respiratory rate (panting) and promote peripheral vasodilation, redirecting blood flow from the internal organs to the body surface. These changes are accompanied by hormonal changes, such as an increase in corticosterone, known as the stress hormone. Electrolyte imbalance, especially a drop in calcium levels, is another worrying factor, as it directly affects the shell quality of the eggs produced.

In order to prevent the negative effects of heat stress, it is essential to adopt appropriate management measures. Provide enough fresh, quality water, ensure adequate ventilation of the shed to remove hot air and the use of cooling systems, such as foggers and pad cooling, are essential strategies.

The use of additives in the diet, such as electrolytes for acid-base balance, antioxidants, vitamins C and E and chelated minerals, also helps in combating heat stress. Dietary supplementation via ethanol yeast cell wall, which has immunomodulatory action, is a highly effective strategy, especially in reducing pro-inflammatory processes and free radicals caused by rising temperatures.

The use of ethanol yeast cell wall can help combat heat stress in laying poultry in a number of ways. Ethanol yeast is an immunonutrient from the cell wall of Saccharomyces cerevisiae yeasts used in the fermentation of sugar cane for ethanol production, rich in mannan oligosaccharides (MOS) and beta-glucans.

There are many beneficial effects of beta-glucans and MOS in mitigating the effects of heat stress:

1. Modulation of the immune response: the MOS and beta-glucans present in ethanol yeast have the ability to modulate the immune response of poultry. They stimulate the activity of macrophages and other defense cells, strengthening the immune system. This is especially important during heat stress, when poultry are more susceptible to disease due to immunosuppression.
2. Maintaining intestinal integrity: heat stress can compromise the integrity of poultry intestinal walls, leading to increased permeability and translocation of pathogenic bacteria. The MOS present in ethanol yeasts have the ability to bind to these pathogenic bacteria, preventing them from adhering to the intestinal wall and reducing colonization. This helps maintain the intestinal integrity and health of the poultry.
3. Balance of the intestinal microbiota: the presence of MOS and beta-glucans helps the growth of beneficial bacteria in the gastrointestinal tract. These beneficial bacteria, such as Lactobacillus and Bifidobacterium, compete with pathogenic bacteria for space and nutrients, helping to maintain a healthy balance of intestinal microbiota. A healthy gut is essential for the proper absorption of nutrients and for maintaining immunity, especially during periods of heat stress.
4. Reduced inflammation: Heat stress can trigger an inflammatory response in poultry’ bodies. The beta-glucans present in ethanol yeast have anti-inflammatory properties, helping to modulate the inflammatory response and reduce the damage caused by excessive inflammation.
5. Improved digestibility and absorption of nutrients: Ethanol yeast helps with the digestibility and absorption of nutrients, especially minerals such as calcium and phosphorus. This is particularly important during heat stress, when food intake is reduced and nutrient absorption can be compromised.

In a study carried out at FZEA-USP (Koiyama et al., 2015), with different inclusions of ethanol yeast in layer feed and under conditions of heat stress (temperatures above 40°C), it was observed that the poultry supplemented with ethanol yeast not only showed better egg production and quality results, but also returned and maintained better production rates after the heat stress period.

The beta-glucans present in ethanol yeasts play a fundamental role in the direct neutralization of reactive oxygen species (ROS), acting as free radical scavengers and protecting cells from oxidative damage. In addition, these compounds are capable of stimulating the poultry’ endogenous antioxidant defenses, activating the expression of genes related to antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). These enzymes are essential for maintaining the oxidative balance in poultry bodies, neutralizing ROS and preventing oxidative stress.

Another important aspect in mitigating the effects of heat is the ability of ethanol yeast to modulate the inflammatory response. Heat stress can trigger an inflammatory process in poultry, which is closely related to oxidative stress. Inflammatory mediators can further stimulate the production of ROS, amplifying oxidative damage. Thanks to the anti-inflammatory properties of beta-glucans, it is possible to reduce inflammation and, consequently, minimize the oxidative stress associated with it.

In conclusion, ethanol yeast is a versatile natural additive that can play a crucial role in mitigating the effects of oxidative stress caused by heat stress in laying poultry. Its multiple mechanisms of action, including direct antioxidant activity, stimulation of endogenous antioxidant defenses, anti-inflammatory effects, maintenance of intestinal integrity and improved feed efficiency, work synergistically to protect poultry against oxidative damage and maintain their oxidative balance during periods of high temperature. The inclusion of yeast in the diet of laying poultry can be an effective strategy for minimizing the negative impacts of heat stress on poultry health and productivity.

By: Fernando Augusto de Souza, zootechnician and product manager at ICC

Learn more about ImmunoWall®, a natural and functional solution resulting from ICC’s technological and scientific improvement, originating from the BetaACTIVE technology that results in a dense yeast cell wall with high stability and low digestibility.