Bigger Hen Comb is an Advantage

The hen with the largest comb gets a bigger dose of sperm resulting in more chicks.

The researchers at the Linkoping University in Sweden show how the hen's comb is bound with the ability to lay more eggs. According to the study, the original wild jungle hen, domestic hens have larger combs as well as denser bones.

This factor affects the egg laying capacity as the hen's bone tissues provide calcium for the eggshells. So greater the bone mass, greater the number of eggs produced.

On tracking this association between comb size and bone mass in chickens the researchers set up a study where the chickens were crossed for several generations. Doing so helped in splitting the genome into smaller regions which allowed the "mapping" of the functions of individual genes.

According to the journal, the eight generation had a strong effect on weight of the comb and also on the bone mass and fertility.

But there was a gradual drop in the genetic variation taking place. It is believed that in the domestic chicken currently there are 40 regions that govern the domestic characteristics.

They have discovered two pleiotropic genes. These are defined as the genes that are linked to each other and influence several characteristics simultaneously.  

The bone growth and the comb are influenced when the production of the cartilage is being regulated. This in turn boosts the egg production.

"The original hens have smaller combs, thinner legs, and lay fewer eggs. When people bred for the characteristic of laying many eggs, the comb grew automatically," Dominic Wright says.

During mating season, males with the most impressive ornaments are favored by females, thereby obtaining healthy sperm and numerous offspring than their competitors.

The scientists, from Linköping, say that the larger the comb of a hen, the bigger dose of sperm she will receive from the rooster, which leads to more eggs.

The scientific journal PLoS genetics published the study.