Genetic regulation of feed intake and energy balance in poultry

Intensive selection by poultry breeders over many generations for economically important production traits such as growth rate and meat production has been accompanied by significant changes in feed intake and energy balance. For example, the modern commercial broiler, selected for rapid growth and enhanced muscle mass, does not adequately regulate voluntary feed intake to achieve energy balance. When given unrestricted access to feed, broilers exhibit hyperphagia leading to an excessive accumulation of energy (fat) stores, making these birds prone to obesity and other health-related problems. Humoral and neural pathways have been identified and studied in mammals that link appetite and energy balance. A series of highly integrated regulatory mechanisms exists for both of these processes involving complex interactions between peripheral tissues and the central nervous system. Within the central nervous system, the brainstem and the hypothalamus play critical roles in the regulation of feed intake and energy balance. Genes encoding key regulatory factors such as hormones, neuropeptides, receptors, enzymes, transcription factors, and binding/transport proteins constitute the molecular basis for regulatory systems that derive from integrated sensing, signaling, and metabolic pathways. However, we do not yet have a complete understanding of the genetic basis for this regulation in poultry. This review examines what is currently known about the regulation of feed intake and energy balance in poultry. A better understanding of the genes associated with controlling feed intake and energy balance and how their expression is regulated by nutritional and hormonal stimuli will offer new insights into current poultry breeding and management practices.