Differential feed intake in mammalian and avian species. Immunization against ghrelin

Ghrelin, a growth hormone releasing peptide, was first isolated from the stomach of rats using "reverse pharmacology". Subsequently, it was isolated from chicken proventriculus, and the preproghrelin gene was characterized in turkeys. In mammals, ghrelin is a 28-amino acid peptide predominantly produced in the stomach that induces increases in feed intake in all species studied to date, including pigs. In contrast to mammals, significantly less is known about the effect of ghrelin on feed intake in turkeys and other avian species. In general, infusion of ghrelin in chickens and Japanese quail inhibits feed intake, while passive immunization against ghrelin increases feed intake. Taken together, the effect of ghrelin on feed intake in mammalian species is the opposite of that in poultry