Sexual dimorphism – a condition where the two sexes have different characteristics, beyond the differences in their sexual organs – is all around us. Differences in plumage, pelage or ornamentation are observed across the animal kingdom with many species also displaying difference in body size and weight. This is a characteristic that in make chickens tends to be bigger and heavier than females.
Appetite and feed intake are largely controlled by a region of the brain which is known as the hypothalamus. Here, there are specialised cells called neurons, which send messages from the brain to the body. For instance, depending on the proteins that are expressed, neurons will tell the body whether the individual is hungry or not. Therefore, the balance of these proteins is crucial to the control of feeding behaviour, growth and body weight.
A study led by Dr Sarah Caughey from The Roslin Institute has looked at what happens in the brain of male and female chickens when they can eat as much as they want as well as when food intake is restricted. The team observed that when they restricted the amount of food birds received, there was an increase in the expression of the protein that drives feeding behaviour – called the agouti-related protein (AGRP). They observed that the expression of proteins that stimulates appetite was higher in males than females. Inversely, they observed no sex differences in the gene expression of anorectic genes. These results could be a useful starting point for investigating further if AGRP is an indicator of growth potential.
The study, which was funded by BBSRC and the Rural & Environmental Science & Analytical Services Division of the Scottish Government, is published in the journal Biology of Sex Differences and has been conducted by researchers at The Roslin Institute, Bioinformatics and Statistics Scotland, Scotland’s Rural College and the School of Natural and Environmental Sciences of the University of Newcastle.