**2. Heat regulation in poultry**

Birds do not have sweat glands and rely on evaporative cooling which is aided by panting to regulate their body temperatures. It has been documented that due to lack of sweat glands in birds, most of the heat loss occurs through respiration [5]. Birds have an extensive air-sac system connected with their lungs which is important in heat regulatory function [5]. In the tropical environments, it has been observed that poultry frequently hold their wings slightly separately when standing to allow air flow through while at the same time extending the heat loss surface area [12]. The birds adopt an extended position when lying down to further increase the surface area. Collectively, these behavioural responses maximise on the surface area of the body in contact with the external environment for heat dissipation [12]. Studies have shown that when chicken are exposed to heat stressful conditions, they spend less time moving and more time resting in the shades or cool places [13]. Birds also manage heat by increasing or decreasing feed and water intake [14]. When the temperatures are high, birds tend to reduce their feed intake while increasing their water intake. The reverse holds when the temperatures are low.

Generally, chicks from many poultry species are not able to efficiently regulate body temperature during early and post hatching period [15]. However, at an early age, the chicks should be provided with right temperatures in the post-hatching stage without which they get chilled and die almost immediately. This underlines the importance of good brooding heat management by provide adequate heat (artificially) for the young chicks. The temperatures should be set at around 35°C in the first week after hatching, with a 3°C weekly reduction until normal ambient temperature of about 23°C - 26°C is attained. Lin et al. [16] proposed that the ideal temperature range for neonatal chicks should be set at between 32 and 35° C. It is important to maintain the right chicks' temperature range when transporting them from hatcheries to avoid overheating or chilling which reduces their post hatch-survival rate [17]. Abdelazeem [18] reported that, high ambient temperatures reduce the chicks' growth rate and feed intake. There is general sluggishness in chicks when temperatures are high [17]. This tends to reduce the feeding time and results in reduced feed intake and consequent poor performance in growth. This problem can be managed by formulating high nutrients density chick feeds which would ensure a good supply of nutrients in the face of low feed intake [19].

It has been observed that free range birds maintain thermal neutrality by hiding under shades during the hot hours of the day while resuming the scavenging in the cool hours of the day [13]. The pattern has also been noted with housed birds which stop feeding during the hot hours of the day and resume feeding in the cool afternoon. This is important for poultry producers to note so as to synchronise their feeding strategies to the behaviour in areas characterised by high ambient temperatures.
