The animal's thermal microenvironment consists of five main components: temperature, air velocity, relative humidity, radiant temperature, and surface temperatures that occur at extreme values, making it difficult for the animal to survive. Food consumption is inversely related to ambient temperature. Feed consumption is altered by changes in ambient temperature; in cold weather, consumption is increased to obtain greater heat production, while in hot weather, food intake is reduced in an attempt to reduce the heat generated by metabolism. The consumption of the amino acid lysine can contribute to feed efficiency by maximising protein synthesis in body tissues and other metabolic intermediates, such as carnitine, which participates in lipid metabolism. However, there is considerable variation in the results of studies on lysine requirements for broiler chickens, which can be explained by differences such as sex, breed, crude protein concentration, and metabolisable energy used in the studies.
