**6. Management of heat stress in poultry flocks**

The primary objective of managing heat stress is to free up nutrients that would have otherwise gone into establishing and maintaining thermal neutrality in animals to be used in growth, maintenance of good health status, production and reproduction. This in turn lead to increased animal productivity and animal production enterprise profitability. The harmful effects of heat stress due to high temperatures are evident and therefore, it is necessary to adopt appropriate strategies to minimise the impacts of high temperatures and enhance production of eggs and chicken meat to meet the growing demand for poultry products [16]. Heat stress in poultry can be reduced by a multi-approaches strategy including modification of the surrounding environment (housing designs, ventilation systems, provision of shaded areas), nutritional management, stocking density management [51] and selection for heat tolerance genes [52, 53]. The approaches can be oriented towards general farm management or dietary manipulation.

#### **6.1 Farm management**

Designing well ventilated poultry house is the first step in the management of heat stress [15]. This can be achieved by installation of efficient air circulation systems in areas characterised by long periods of high ambient temperature. Butcher and Miles [54] notes that this not only ensures appropriate air movement in the poultry house in provision of sufficient air movement for convective heat loss in hot conditions but also aids in maintenance of appropriate air quality in terms of oxygen, carbon dioxide, ammonia and humidity. In free-range production system poultry producers should avail shades by planting shrubs around the homestead or building a shade. This creates a conducive environment for the scavenging chicken to shelter during the hot periods especially in the tropics. Grass cover around the poultry shed is a way to reduce the heat load on birds, similar is the case with plantation of trees around the shade [15]. Furthermore, a shiny surface on the roof can reduce heating of the house from solar radiation. Provision of appropriate shelter, shade, sprinkling systems and ventilation are the various management strategies employed. To avoid compounding the effect of heat stress in poultry flocks, additional stress which could result from routine handling procedures such as vaccination, beak trimming, and transfers. If it is necessary, they should be effected during the cool hours of the day and if possible at night while making sure the birds are held gently and calmly.

Findings presented in a study by Bhadauria [14] indicates that heat stress can be reduced or eradicated by ensuring that birds are provided with the recommended floor space which ensures that there is no overstocking. A floor space of 0.06 m<sup>2</sup> / bird for birds weighing 1.7 kg, 0.13 m<sup>2</sup> /bird for those weighing 3.5 kg both of which translate to a density of 27.8 kg/m<sup>2</sup> .

Besides the direct negative impacts of heat stress in poultry flocks, it has also been noted that hatchery eggs should be transported and stored in air-conditioned environment so as to maintain their quality [55]. It is noteworthy that good quality eggs have a high hatchability. Consumer eggs also need to be transported in an environment not detrimental to their quality as this will hamper their market price and preference [56]. Chicken meat is highly perishable under high temperatures and for that reason should maintained in a cold chain from slaughtering to the market to avoid loss of quality [57].

Animal breeding (selection) for chicken lines that perform better in environments characterised by high ambient temperatures has been identified as a potential heat stress management strategy [11, 52, 53]. This can be achieved by considering genes identified as having potential to be involved in thermal regulation. For example, the naked neck gene and the frizzle gene have been suggested in several literature potential genes to develop breeds that can cope with high ambient temperatures [11]. Other studies have also found that poultry breeds with superior thermotolerance can be developed by using thermo-tolerant genes such as frizzle gene, naked neck genes, dwarf gene and polymorphisms in heat shock proteins (HSP) genes using marker assisted selective breeding [52, 53]. The broiler lines have a high metabolic rate and are more susceptible to heat stress.

#### **6.2 Dietary management**

High ambient temperatures negatively impact nutrients intake and utilisation in chicken through different pathways [19, 27]. However, irrespective of the pathway, the net effect is poor performance in terms of production, reproduction and health. For example, results from the study carried out by Saeed et al. [15] indicated that the gut microorganisms' population and diversity was negatively affected by heat stress. The study findings indicated that the problem can be counteracted by supplementing the chicken with probiotics which have potential to restore the population and diversity in the jejunum and caecum thus resulting to microbial balance while maintaining the natural stability. This implies that prebiotics and probiotics can help in reducing heat stress and improving performance in poultry birds.

The study by Sohail et al. [19] showed that chronic heat stress reduced broiler production performance by interfering with the intestinal microarchitecture as

**197**

stress condition.

*The Effects of Heat Stress on Production, Reproduction, Health in Chicken and Its Dietary…*

performance in environment characterised by high temperatures.

well as increasing the adrenal hormone concentrations, however, this challenge was counteracted by use of prebiotics like the mannan-oligosaccharides and probiotic mixture which reduced/eradicated the negative impacts caused by the anatomical and physiological changes. An analysis of the existing literature such as [19, 25, 49, 58–61] on potential approaches has shown that nutritional manipulation as well as inclusion of feed additives such as vitamins, antioxidants, probiotics, prebiotics has potential to eradicate and/or reduce the negative impact of heat stress on chicken performance. For instance, findings presented in a study by Ranjan et al. [25] showed that varying energy concentration in chicken diets, adjusting feeding times, manipulating protein to energy ratio in chicken feeds, wet feeding and using automated drinkers raised at an optimal height positively impacted on chicken

The investigation by Ranjan et al. [25] concluded that birds should be supplied with high density diets to compensate for the lost feeding time and the decreased feed intake in response to high environmental temperature. The diets should be high in amino acids, vitamins, electrolytes and sodium bicarbonate to compensate for mineral lost through increased panting. Ratriyanto et al. [61] reported that during heat stress supplementing laying quails with feed additives such as the Betane at a rate of 0.06–0.12% increased feed intake, protein and energy ratio as well as improving the egg quality variables. It is noteworthy that addition of vitamins A, E and zinc is beneficial in increasing antioxidant levels as oxidative balance is disturbed in heat stressed birds [49]. The study indicated that supplementing chicken diets with vitamin E alleviated many negative effects that occur during heat stress. Crozier et al. [58] demonstrated that use of phytochemicals with antioxidant activity helps to solve heat stress in chickens. Phytochemicals like polyphenols, a vital secondary metabolite found in certain plants serve as a means to reduce heat stress. Furthermore, it has been found that polyphenols have the ability to boost the expression of heat shock proteins (HSP) and antioxidant enzymes which restrain reactive oxygen species in the body of poultry birds [62]. Inclusion of vitamins C and E, carotenoids and microelements such as zinc, copper and selenium in chicken diet act as antioxidant non-enzyme system which helps in during stressful conditions [62]. Study by Yosi et al. [60] showed that supplementation of minerals like potassium chloride (KCl) in poultry drinking water are beneficial effect under heat

Further, findings in the research by Sahin et al. [59] demonstrated that feeding layers late in the evening in environments constrained by high ambient temperatures resulted in improved laying percentage and egg shell quality. This would be explained by the increased nutrients intake that would support improved laying and high-quality egg shell as calcium is an integral component of chicken feeds. Literature search and review indicates that early morning or late evening chicken feeding, when the ambient temperatures are low, is a potential strategy in managing heat stress in poultry production. Wet feeding is also used in managing heat stress as it results in compensation of the water lost when birds pants, which always increase with increase in ambient temperature [19, 27]. Besides, drinking water should be placed in the shades to supply the body requirements [27]. Since water plays a key role in regulating the body temperature of birds water tanks should be located in a shade and insulated [19]. The personnel working within the poultry houses should ensure at all times that there is sufficient water flowing in the drinkers. The findings presented in Gous and Morris [27] and Sohail et al. [19] indicate that birds water intake increases by 1.2% for every 1°C rise in the temperature range of 22–32°C and 5% for 1°C rise in the temperature range of 32–38°C rises which are able to control body temperature in hot environments. Optimal utilisation of increased nutrients and water intake has to be accompanied with a good supply of oxygen [14]. This

*DOI: http://dx.doi.org/10.5772/intechopen.97284*

#### *The Effects of Heat Stress on Production, Reproduction, Health in Chicken and Its Dietary… DOI: http://dx.doi.org/10.5772/intechopen.97284*

well as increasing the adrenal hormone concentrations, however, this challenge was counteracted by use of prebiotics like the mannan-oligosaccharides and probiotic mixture which reduced/eradicated the negative impacts caused by the anatomical and physiological changes. An analysis of the existing literature such as [19, 25, 49, 58–61] on potential approaches has shown that nutritional manipulation as well as inclusion of feed additives such as vitamins, antioxidants, probiotics, prebiotics has potential to eradicate and/or reduce the negative impact of heat stress on chicken performance. For instance, findings presented in a study by Ranjan et al. [25] showed that varying energy concentration in chicken diets, adjusting feeding times, manipulating protein to energy ratio in chicken feeds, wet feeding and using automated drinkers raised at an optimal height positively impacted on chicken performance in environment characterised by high temperatures.

The investigation by Ranjan et al. [25] concluded that birds should be supplied with high density diets to compensate for the lost feeding time and the decreased feed intake in response to high environmental temperature. The diets should be high in amino acids, vitamins, electrolytes and sodium bicarbonate to compensate for mineral lost through increased panting. Ratriyanto et al. [61] reported that during heat stress supplementing laying quails with feed additives such as the Betane at a rate of 0.06–0.12% increased feed intake, protein and energy ratio as well as improving the egg quality variables. It is noteworthy that addition of vitamins A, E and zinc is beneficial in increasing antioxidant levels as oxidative balance is disturbed in heat stressed birds [49]. The study indicated that supplementing chicken diets with vitamin E alleviated many negative effects that occur during heat stress. Crozier et al. [58] demonstrated that use of phytochemicals with antioxidant activity helps to solve heat stress in chickens. Phytochemicals like polyphenols, a vital secondary metabolite found in certain plants serve as a means to reduce heat stress. Furthermore, it has been found that polyphenols have the ability to boost the expression of heat shock proteins (HSP) and antioxidant enzymes which restrain reactive oxygen species in the body of poultry birds [62]. Inclusion of vitamins C and E, carotenoids and microelements such as zinc, copper and selenium in chicken diet act as antioxidant non-enzyme system which helps in during stressful conditions [62]. Study by Yosi et al. [60] showed that supplementation of minerals like potassium chloride (KCl) in poultry drinking water are beneficial effect under heat stress condition.

Further, findings in the research by Sahin et al. [59] demonstrated that feeding layers late in the evening in environments constrained by high ambient temperatures resulted in improved laying percentage and egg shell quality. This would be explained by the increased nutrients intake that would support improved laying and high-quality egg shell as calcium is an integral component of chicken feeds. Literature search and review indicates that early morning or late evening chicken feeding, when the ambient temperatures are low, is a potential strategy in managing heat stress in poultry production. Wet feeding is also used in managing heat stress as it results in compensation of the water lost when birds pants, which always increase with increase in ambient temperature [19, 27]. Besides, drinking water should be placed in the shades to supply the body requirements [27]. Since water plays a key role in regulating the body temperature of birds water tanks should be located in a shade and insulated [19]. The personnel working within the poultry houses should ensure at all times that there is sufficient water flowing in the drinkers. The findings presented in Gous and Morris [27] and Sohail et al. [19] indicate that birds water intake increases by 1.2% for every 1°C rise in the temperature range of 22–32°C and 5% for 1°C rise in the temperature range of 32–38°C rises which are able to control body temperature in hot environments. Optimal utilisation of increased nutrients and water intake has to be accompanied with a good supply of oxygen [14]. This

implies that there is need to enhance air flow in the chicken houses. In free range systems where ambient temperatures are high it would be advisable to place the supplemental feed near or under the shades [19].
