CHAPTER ONE 1.0 INTRODUCTION Human diets in tropical countries such as Nigeria are most often protein-poor, both quantitatively and qualitatively (Okeke et al., 1985; Ojewola, et al., 2004). For instance, the contemporary average per capita protein consumption in Nigeria is estimated at 7-10g (Oluremi et al., 2008; Okuneye, 2002). This estimate falls far below the FAO (1997) recommendation of 35g/caput/day. Meanwhile, it should be borne in mind that the Nigerian population on the other hand, continues to rise. Current demographic figures show that the total head count overshoots 140 million at a 3.0% annual growth rate (BBC News, 2006; Nigerian News, 2006), without a corresponding livestock population to match (FAO, 2005). To stabilize this situation, no improvement could be made in this country without an increase in food crops, livestock and fish farming. Even then, from the point of view of quality protein consumed, animal proteins by far outweigh proteins from crop sources (Obioha, 1992). Regrettably, there is a perennial low intake of animal products such as meat, milk and eggs in Nigeria (Onyimonyi, 2002). Unfortunately, these animal products are the major sources of high quality proteins. The implication is that, the nutritional status of the Nigerian population and economic development are inextricably linked. This is a clear indication of the inability of the traditional system of animal agriculture to meet the protein needs of Nigerians creating an avenue for protein malnutrition to persist! The immediate remedy would thus, involve the massive production of animals with short reproductive cycles such as poultry, pigs and rabbits. But when a quick means of significantly increasing turnover rate thereby modifying farm income and improving animal protein in the human diet is the objective, then poultry becomes the animal of choice (Emeruwah, 1999; Ojewola, et al., 2004). Apart from these dimensions, Obioha (1992) has earlier demonstrated that poultry are excellent feed converters. Carew et al. (2007) have also shown that, poultry do not suffer social infringement on consumer acceptability like other livestock species such as pigs. The foregoing has triggered the rising demand for poultry products like eggs and meat given their palatability and high nutritional value (CTA, 1987; Ojewola, et al., 2005). These attributes among others, make the poultry industry stand tall amidst rival livestock producing ventures. However, for poultry to perform its ascribed roles, it is necessary to closely scrutinize the environmental factors that have the capability of frustrating their genetic potentials. Nigeria being a humid tropical country is associated with a myriad of these environmental factors. Sinkalu et al. (2008) have listed these environmental stressors as: deprivation of food and water, high ambient temperatures (AT), relative humidity (RH), high velocity, noise, motion, overcrowding, vibration and mishandling. Among these factors, high AT and RH are the most important meteorological stress factors adversely affecting poultry in general, and laying hens in particular (Asli et al., 2007; Ayo and Sinkalu, 2007; Ayo et al., 2005a; Ramnath et al., 2008). The ideal temperature (conventionally referred to as the zone of thermo neutrality) under which the performance of laying hens is not adversely affected by temperature has been earlier identified by Oluyemi and Roberts (2000) as 12.8-26.00C. CTA (1987) has however given the thermo neutral zone to be 16 -200C. Anderson and Carter (2007) on the other hand identified the range of thermo neutrality as 12.8 – 23.9 0C. Recent field work by Imik et al. (2009) has narrowed the thermo neutral zone of laying hens to 18- 220C.
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