MECHANISMS REGULATING FOOD INTAKE, ENERGY BALANCE AND BODY WEIGHT IN POULTRY

Authors: Richards, Mark; Proszkowiec-Weglarz, Monika

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2007
Publication Date: 7/1/2007
Citation: Richards, M.P., Proszkowiec-Weglarz, M. 2007. Mechanisms regulating feed intake, energy expenditure, and body weight in poultry. Poultry Science. 86(7):1478-1490.

Interpretive Summary: One of the primary goals of poultry producers today is to improve the efficiency and profitability of meat production. To continue to meet this goal, poultry breeders have placed a major emphasis on the selection of lines of chickens and turkeys that grow faster and produce more meat than previous generations. Unfortunately, along with improvements in these economically important traits have come some unwanted changes in feed intake and body composition. Commercial lines of broiler chickens and turkeys tend to overeat when given free access to feed. This can lead to an excessive accumulation of fat and a variety of health-related problems if their access to feed is not strictly limited throughout their entire lifecycle. Abdominal fat is now regarded as a main source of waste by poultry processors and thus a major contributor to decreased production profitability. In order to improve this situation, it is important to first understand the underlying genetics of the mechanisms that regulate appetite and energy balance in poultry. This manuscript discusses what we currently know about the regulation of feed intake, energy balance, and body weight in poultry. A better understanding of the genes associated with controlling appetite 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. This information is intended for use by researchers studying the control of appetite and body weight in avian species, as well as, poultry producers in formulating new genetic selection and feeding strategies for commercial poultry flocks.

Technical Abstract: In order to maintain a constant body weight, food intake and energy expenditure must be coordinated and tightly regulated. This may not hold true for some poultry species intensively selected for such economically important traits as growth and meat production. For example, the modern commercial broiler breeder does not adequately control voluntary food intake to meet its energy requirements and maintain energy balance. As a consequence, feeding must be limited in these birds to avoid over consumption and excessive fattening during production. It is important to determine a genetic basis to help explain this situation and to offer potential strategies for producing more efficient poultry. This review summarizes what is currently known about the control of food intake and energy balance at the gene level in birds. Highly integrated regulatory systems have been identified that link the control of feeding with energy status. How such systems function in poultry is currently being studied. One example recently identified in chickens is the AMP-activated protein kinase pathway that links energy sensing with modulation of metabolic activity to maintain energy homeostasis at the cellular level. In the hypothalamus, this same pathway may also play an important role in regulating food intake and energy expenditure commensurate with perceived energy needs. Genes encoding key regulatory factors such as hormones, neuropeptides, receptors, enzymes, and transcription factors are some of the types of molecular components that comprise intricate networks of signaling, sensing, and metabolic pathways linking peripheral tissues with the central nervous system. Moreover, coordinate expression of specific gene groups can establish functional pathways that respond to and are regulated by such factors as hormones, nutrients, and metabolites. Thus, with a better understanding of the genetic basis for regulating food intake and energy balance in birds important progress can be made in developing, evaluating, and managing more efficient commercial poultry lines.