Effective poultry heat stress management on the farm relies on a multifactorial approach to improve air flow and ventilation, spacing, dehumidification and evaporation, feeding strategies and nutritional management. To uplift the effects of these approaches, an efficient sustainable tool is adding quality yeast postbiotic in feed to protect birds’ against heat stress.
Poultry R&D Manager
Phileo by Lesaffre
Global Poultry Program Manager
Phileo by Lesaffre
Heat stress causes substantial economic losses for broiler producers. In the USA, the average yearly losses associated with heat stress range from $128 to 165 million, and in China heat stress greatly contributes to the $2.7 billion in losses recorded in poultry livestock. Modern, fast-growing poultry genotypes exhibit higher metabolic activity, which increases heat production and makes broilers highly susceptible to heat stress.
HEAT STRESS – AN INSIDIOUS THREAT
Heat stress is triggered by a combination of high temperature and relative humidity levels, as both impact the ability of the birds to regulate body temperature through heat loss. Temperature and humidity data is often used to calculate the temperature humidity index (THI), which is a valuable measure to assess when birds are becoming heat-stressed (Figure 1).
Heat stress’ harmful effects are myriad, from overall body weight decreases as feed intake drops, to falls in egg production rates and thinner eggshells due to reduced calcium uptake, to increases of up to 25% in feed conversion ratio.
HEAT STRESS DISRUPTS HOMEOSTASIS
These negative effects on poultry weight gain and feed conversion result from a complex cascade of physiological changes during increasing heat stress. In an effort to reduce body temperature and maintain thermoneutrality, the hypothalamic-pituitary-adrenal (HPA) axis of the neuroendocrine system aims to regulates body temperature via the production of T3 and T4 thyroid hormones. The initial functions of T3 and T4 hormones is to modulate protein synthesis for broiler growth; under heat stress these hormones are “mobilized” to regulate and balance body temperature. Furthermore, once a bird can no longer maintain its body heat balance, the birds spend more time resting and with wings aloft, water consumption increases, and feed intake decreases. Simultaneously, the bird’s blood flow is partially redirected from the body core to the periphery. Decreased blow flow to the internal organs—such as the gut—creates oxygen deprivation and reduces nutrient intake, and can increase gut permeability, thus creating a leaky gut. Under these conditions, pathogenic bacteria (such as E.coli and Clostridium perfringens) and their endotoxins (lipopolysaccharides or LPS) can traverse the gut wall and enter the bloodstream, potentially inducing fever, blood coagulation, decreased blood pressure, and eventually multiple organ failure and death. As a consequence, corticosterone release can increase which results in negative effects on both the thyroid gland and immune system, rendering the bird more susceptible to infection and negatively affecting bird performance.
INTEGRATED EFFICIENT HEAT STRESS MANAGEMENT
To protect the birds against heat stress, poultry producers outfit houses with proper equipment (e.g. sprinklers or foggers), implement appropriate feeding and nutritional strategies. To complete the picture, poultry producers are searching for additional cost-effective, sustainable solutions, especially under current cereal and energy (e.g. electricity) turbulent supply and price which heavily impact poultry production cost.
Numbers of studies, conducted worldwide, have demonstrated that the premium-quality yeast postbiotic, Safmannan® (here after called “yeast postbiotic”) has the ability to decrease body temperature, modulate thyroid hormone and corticosterone secretions, preserve gut morphology and improve birds’ performance under different levels of heat stress.
To avoid leaky gut, one of the frequent heat stress induced gut issues, it’s crucial to preserve tight junctions which are essential to intestinal barrier maintenance by tightly connecting epithelial cells together. A study was conducted in Japan recently to explore the effects of yeast postbiotic on poultry gut morphology preservation under severe acute heat stress. The expression levels of two gut tight junction proteins (ZO-1 and Claudin-5) were assessed under both normal conditions, and conditions of severe acute heat stress (THI of 32) with and without 250 g/t Safmannan® supplementation in broilers’ diet. In animals undergoing heat-stress, these protein levels nearly halved compared to controls, and thus could contribute to a leaky gut phenotype. Nutritional supplementation with the yeast postbiotic enabled the reversion of junction proteins to near negative control levels, indicating a return to normal gut integrity. A robust gut barrier will also reduce liquid loss from the bloodstream into the gut, as seen by drier feces.
Heat stress can trigger proliferation of the enteropathogenic Clostridium perfringens bacteria in the poultry gut resulting in chronic inflammation and consequently poor production performance. A recent trial in the Middle East investigated the effects of adding 500 g/t Safmannan® in broilers’ feed inoculated with an infectious dose of Clostridium perfringens, under natural heat stress conditions. At day 30, supplemented birds demonstrated a 2-Log reduction in microbial load compared to unsupplemented controls (p=0.01), thus improving their ability to resist opportunistic infection under heat stress.
Different studies have demonstrated that the yeast postbiotic can reduce the effects of heat stress on poultry via hormonal modification. Sohail et al. subjected Ross 708 broilers to chronic severe heat stress (THI 33) for 42 days. At 21 and 42 days, circulating corticosterone concentration (biomarker of heat stress) was measured in control groups and those experiencing heat stress, either supplemented or not with 500 g/t Safmannan®. At both time points (Figure 2), the heat stressed control group had significantly higher corticosterone concentrations than negative control group and the heat-stressed-supplemented group (p<0.05). Postbiotic supplementation is therefore able to normalize corticosterone concentrations in heat stressed birds, thereby reducing the harmful effects of corticosterone on immunity and growth. Another study conducted in Mexico examined thyroid stimulating hormone (TSH) and T4 hormone levels in Cobb 500 birds under chronic severe heat stress conditions (THI = 33) either supplemented or not with 500 g/t postbiotic. At 35 days, compared to the control group, the birds in the yeast postbiotic group have significantly decreased levels of the regulator TSH and increased levels of the metabolic regulator T4 (p<0.05), thereby improving energy metabolism and growth.
In Arbor Acres broilers, a trial in China (Figure 3) proved that 250 g/t Safmannan® supplementation throughout chronic heat stress (THI = 32) helped to significantly lower body temperatures by 0.5°C when measured at 42 days compared to unsupplemented birds (p<0.05). Furthermore, postbiotic supplementation also showed increased in daily weight gain comparable to non-heat stressed controls (p<0.05).
THE GOLD-STANDARD YEAST POSTBIOTIC – KEY ELEMENT IN THE ARSENAL TO COMBAT HEAT STRESS
Most of the projected growth in poultry production will occur in tropical zones spanning Asia, Africa, and Latin America, all of which are at a higher risk of heat stress. With global warming, heat stress becomes a very prominent issue affecting both bird welfare and producer economical profit. Anticipating heat stress by implementing integrated approach including housing, feeding regimes and nutritional strategies, ensures consistent production while maintaining animal living conditions to improve economic return. With a proven efficacy in plenty of studies performed worldwide, Safmannan® plays a key role in managing heat stress in poultry. The evidence provided above demonstrates that Safmannan® is a gold-standard yeast postbiotic both capable of shielding birds from the worst effects of heat stress, but also positively influencing production parameters via multiple mechanisms of action in reinforcing gut morphology and function and via hormone modulation.
