A Hormone for
Hunger in Humans May Leave Chickens Feeling Full
April 21, 2003
Last year, foreign scientists
discovered that while a hormone called ghrelin may boost the appetite of
humans, the chicken version of the hormone may have the opposite effect in
broiler birds. Now Agricultural Research
Service scientists are looking for the genetic components of ghrelin that
govern feed intake and calorie expenditure in chickens.
Egg-laying chickens and broiler birds exhibit a significant difference in
appetites, with broilers having voracious ones. Animal scientist Mark Richards,
of the ARS Growth Biology
Laboratory in Beltsville, Md., is looking at the gene for ghrelin in each
of these bird types for clues to the difference in appetite. Richards and other
scientists have already sequenced portions of the gene that produces the
ghrelin hormone, and they are now exploring the genetic differences between the
two types of chickens.
Poultry producers have intensively selected for lines of chickens and
turkeys that grow faster and produce more meat than previous generations.
Unfortunately, along with these improvements have come some unintended changes
in feed intake and body composition. Modern commercial strains of broiler
chickens tend to overeat when given free access to feed. This can lead to
obesity and other health-related problems if the birds are not put on a strict
Within the central nervous system, specific centers of the brain--the
brainstem and the hypothalamus--play critical roles in the regulation of
appetite and metabolism. Both food intake and energy balance are biological
functions that are orchestrated by intricate biochemical processes involving
enzymes, hormones and other types of proteins, each the product of a unique
Scientists do not yet have a complete understanding of the genetic basis for
the regulation of these functions in chickens. A better understanding of the
genes associated with controlling feed intake and energy balance and how they
are regulated by nutritional and hormonal inputs should bring new insights for
improving poultry breeding and management practices.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.