At the ARS Animal Biosciences and Biotechnology Laboratory in Beltsville, Md., animal scientists Monika Proszkowiec-Weglarz and Mark Richards, along with research leader John McMurtry and Penn State University collaborator Ramesh Ramachandran, recently identified and sequenced genes responsible for regulating both energy use by individual cells and the food intake of birds. They also showed that the genes function in different tissues throughout the body of the broiler chicken.

This important biochemical pathway, previously discovered in other animals, maintains energy balance in the bird’s body. A key component of the pathway is an enzyme called AMP-activated protein kinase, or AMPK.

In all animals, obesity results from an imbalance that occurs when more food energy (calories) is consumed than the body actually needs. The excess energy is stored mostly as fat. Over the years, in response to a growing worldwide consumer demand, poultry breeders have bred chickens that grow faster and produce more meat. But modern broiler/breeder chickens don't adequately balance their feed consumption to match their energy requirements. When these birds are given unrestricted access to feed, they will overeat and become obese.

AMPK plays a central role in sensing cellular energy levels. It begins a series of events that affect food intake and metabolism of fat, carbohydrate and protein. According to Proszkowiec-Weglarz, AMPK is really a “molecular fuel gauge” and a master metabolic regulator in cells. It responds to fluctuations in the levels of cellular energy and of specific nutrients and hormones outside the cells.