**3. Effect of environment on poultry nutrition and production**

Various environmental factors including temperature, light, rainfall, humidity and altitude collectively impact on an animal's nutrition [14]. The respective factors can impact on the intake singly or cumulatively. There is an inverse relationship between energy requirements and effective temperature which subsequently affects feed intake mechanisms related to circulating levels of blood components [20, 21]. It has also been documented that high temperatures above the critical thresholds leads to reduced feed intake, lower feed conversion efficiency and lower body weight [19]. It has been observed that heat from an external source or from specific dynamic action of feed has effect on the rostral cooling centre of the hypothalamus which results to a stimulation of the medial satiety centre which in turn inhibit the lateral appetite centre [16]. This results to a decrease in feed intake and subsequent lower the production and/or reduced reproduction efficiency. Broiler birds when exposed to high solar radiation are coupled with depression of chemical composition and meat quality [22].

Birds experiencing heat stress usually pant with their mouths open, elevated wings and have higher tendencies of squatting near the ground [17]. It has been reported that laying flock when exposed to high temperatures shows disturbance in acid -base balance in the blood as a result of hyperventilation, there is excessive loss of CO2 from their lungs due to gasping [20]. The lowered amount of CO2 in blood leads to a rise in blood PH causing calcium ions to drop in blood that would have been utilised by the shell gland resulting to poor egg quality [23]. It is noteworthy that increased panting in poultry is a sign of heat stress. Other noticeable indicators of heat stress include elevated respiratory rate, and restlessness which lead to increased loss of body fluids and therefore dehydration [20]. The birds also tend to drink more water in order to cool their bodies while feed intake reduces drastically. These adversely affect the efficiency of meat production and the meat quality especially in the exotic birds not adapted to the tropics. Zhang et al. [24] demonstrated that, when broiler chickens were exposed to high temperature during the growing phase, it resulted to poor meat characteristics and loss of quality. Ranjan et al. [25] observed that when broiler birds are exposed to high ambient temperatures during the growth phase tended to result in poor meat characteristics as well as loss of storage quality [22]. Heat stress reduced the proportion of breast meat while increasing the proportion of fat in the carcass. Zeferino et al. [26] further noted that when broilers were exposed to high ambient temperatures during the finishing phase, the carcass lost quality characters related to consumer preferences such as colour, tenderness and shelf life due to increased meat PH. High altitude areas ranging from 2,900–3,900 m are characterised by hypoxia, lower air pressure and lower ambient temperature compared with the lower altitude areas. This in turn affects nutrients partitioning which has impact on productivity and profitability. More nutrients are shifted to deal with the cold and the low oxygen levels which subsequently affects nutrients digestibility and allocation of the nutrients to various biological processes [26]. In all cases, production and reproduction performances are affected negatively.

It is evident that temperature primarily affects production of poultry meat and eggs through increased or decreased feed intake. Various authors such as [20, 21] reported that there was notable reduction in egg production in hot environments due to decrease in feed intake, decreased digestibility of different diet components and reduced uptake of available nutrients [19, 27]. Generally, feed intake starts to decline when chickens are kept in an environment characterised by temperatures above 27°C. At 35°C there is a significant decrease in feed intake. Besides, studies have shown that the reduction in intake is accompanied by decrease in feed conversion ratio. Optimal nutrient intake and utilisation is a key factor in weight gain and egg production which are the key drivers of poultry enterprise productivity and profitability. Any factor that affect the intake is important to producers whose objective is production optimisation and profit maximisation. In a scenario where

**193**

poor egg quality.

ity meat negatively [34].

**4. Heat stress and reproduction**

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

the intake is negatively impacted by high ambient temperatures, producers can counter the reduction in feed intake by formulating high density diets. Besides, feed management can be accomplished through housing chicken in well ventilated pens especially in areas characterised by high ambient temperatures [15]. Poultry production systems in environments characterised by high ambient temperatures have reported steep rise in culled birds resulting from reduced productivity and death emanating from heat stroke. This loss makes such systems unproductive and

The high temperatures further cause a decrease in the egg shells thickness and weight [28] in laying hens. This leads to increased egg breakage during the storage and transportation. Generally, egg quality during storage decreases gradually with increasing temperatures [29]. Low temperatures have no impact on egg shell thickness while low temperatures have been shown to increase feed conversion ratio. Climatic stress in laying hens leads to a reduction both egg production and quality [30]. The notable decrease in egg production can be explained by the imbalance between calcium-oestrogen and the reduced Haugh Unit of the albumen detected in birds subjected to heat stress [31]. This leads to a reduced yolk size, albumen consistency and normal calcium deposits on the egg shells. Birds tend to spend more time resting rather than eating which negatively impact on the available nutrients to satisfy production and reproduction processes and outcomes [32]. Climatic stressors trigger the behavioural, physiological and immunological responses which have detrimental consequences on production and quality. Heat stress shifts more energy to maintenance and acclimatisation functions at the expense of growth thus resulting to decreased body weight gain when subjected to heat stress. Lara and Rostagno [31] noted that the negative effects on production and quality emanate from the decreased feed intake, reduced feed digestibility, low plasma protein and calcium levels. Oguntunji and Olufemi [30] observed that egg sizes which affects their market value decreases with a decrease in feed intake. Scavenging poultry is affected more as the birds spend more time under shades when they should be

harvesting nutrients necessary in production and reproduction [33].

It is noteworthy that exposure of day-old chicks to high ambient temperatures during transportation, which has been identified as one of the leading causes of chicks' mortality, leads to exhaustion and death [15]. This means there are less birds available for production and reproduction. Day old chicks should be transported in well ventilated trucks and in equipment that ensure air circulation while at the same time avoiding overcrowding. Besides the need to transport the chicks in appropriate temperature range, high temperatures during transportation of broilers from the farm to the slaughter and processing facilities have been shown to impact the qual-

Studies have shown that high ambient temperatures, outside the thermal-neutral zone results to negative effects on chicken biological processes. The optimal temperature ranges between 12°C -26°C. Research findings presented in Ebeid et al. [35] suggest that reproduction of the animal is highly affected with high temperatures. The study shows that when white leghorn hens are subjected to high temperatures there is a decline in reproductive activity leading to reproductive failure and

Fouad et al. [34] further showed that increased environmental temperatures affect all stages of semen production. Slight elevation of the environmental temperature during the early phase of semen production has been shown to stimulate

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

unprofitable.

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

the intake is negatively impacted by high ambient temperatures, producers can counter the reduction in feed intake by formulating high density diets. Besides, feed management can be accomplished through housing chicken in well ventilated pens especially in areas characterised by high ambient temperatures [15]. Poultry production systems in environments characterised by high ambient temperatures have reported steep rise in culled birds resulting from reduced productivity and death emanating from heat stroke. This loss makes such systems unproductive and unprofitable.

The high temperatures further cause a decrease in the egg shells thickness and weight [28] in laying hens. This leads to increased egg breakage during the storage and transportation. Generally, egg quality during storage decreases gradually with increasing temperatures [29]. Low temperatures have no impact on egg shell thickness while low temperatures have been shown to increase feed conversion ratio.

Climatic stress in laying hens leads to a reduction both egg production and quality [30]. The notable decrease in egg production can be explained by the imbalance between calcium-oestrogen and the reduced Haugh Unit of the albumen detected in birds subjected to heat stress [31]. This leads to a reduced yolk size, albumen consistency and normal calcium deposits on the egg shells. Birds tend to spend more time resting rather than eating which negatively impact on the available nutrients to satisfy production and reproduction processes and outcomes [32]. Climatic stressors trigger the behavioural, physiological and immunological responses which have detrimental consequences on production and quality. Heat stress shifts more energy to maintenance and acclimatisation functions at the expense of growth thus resulting to decreased body weight gain when subjected to heat stress. Lara and Rostagno [31] noted that the negative effects on production and quality emanate from the decreased feed intake, reduced feed digestibility, low plasma protein and calcium levels. Oguntunji and Olufemi [30] observed that egg sizes which affects their market value decreases with a decrease in feed intake. Scavenging poultry is affected more as the birds spend more time under shades when they should be harvesting nutrients necessary in production and reproduction [33].

It is noteworthy that exposure of day-old chicks to high ambient temperatures during transportation, which has been identified as one of the leading causes of chicks' mortality, leads to exhaustion and death [15]. This means there are less birds available for production and reproduction. Day old chicks should be transported in well ventilated trucks and in equipment that ensure air circulation while at the same time avoiding overcrowding. Besides the need to transport the chicks in appropriate temperature range, high temperatures during transportation of broilers from the farm to the slaughter and processing facilities have been shown to impact the quality meat negatively [34].
