The study, which was carried out by The Roslin Institute at the University of Edinburgh in Scotland, aimed to establish why some birds are less sensitive to fullness, which leads them to overeat.
The researchers compared how a fast-growing strain of chicken, a slow-growing strain of chicken and a cross of both strains processed the protein cholecystokinin (CCK), which plays a key role in sending signals of fullness to the brain. They found that the faster-growing breeds were less able to recognise the protein, leading to overeating and excessive growth.
The study pointed out that these differences could date back thousands of years to when birds were first domesticated and bred selectively for their size.
“The findings shed greater light on food intake in birds and help us understand why some breeds – in general the faster-growing types of chickens – are more insensitive to feelings of fullness than others,” said Dr Ian Dunn, who led the study.
“All species regulate their appetites to make sure the amount of food taken in is just right to maintain body weight and fat content. Our research has shown there is genetic variation in the interpretation of biological signals sent relating to being full. This also affects what would be considered to be the natural body weight of chickens.”
It is hoped the study, which was published in the American Journal of Physiology – Endocrinology and Metabolism, will make it easier to develop diets for birds prone to overeating, which in turn should improve welfare by preventing excessive growth.