Blind chickens lay more eggs, Ontario researcher says

Sure, love is blind, but who knew about breakfast?

Researchers at the University of Guelph in southwestern Ontario have discovered that a strain of naturally blind chickens produces more eggs than their sighted counterparts a finding that could help farmers improve commercial egg yields.

Scientists found that the way the blind chickens known as Smoky Joes respond to light gives them an advantage when it comes to laying eggs.

Prof. Gregoy Bedecarrats made the discovery after he began studying reproduction patterns of the blind chickens in 2004 to learn how light influences egg production. He said the research could prove valuable to farmers, who could increase egg yields by altering lighting techniques.

"We could figure out some way to alter the lighting so that it biologically prompts the chickens to produce more," Bedecarrats said.

The professor of animal poultry science said the Smoky Joes lack retinas, which forces the birds to process light in a different way, giving them an edge when it comes to egg laying.

"These chickens reach the peak of egg production one to two weeks before the normally sighted birds, and produce around 10 per cent more eggs," Bedecarrats said.

"At the basic level, it's because Smoky Joes are unable to process specific wavelengths in light because they lack retinas, which inhibit sexual maturation. Since they mature faster, they are also able to produce eggs sooner, and for some reason, at a higher quantity."

In most commercial farms in Canada, White Leghorn chickens are bred to produce large quantities of eggs year-round through a process of photostimulation.

Using incandescent light, such as regular light bulbs, breeders can stimulate ovary maturity in chickens by exposing the birds to light for a certain number of hours daily to mimic daylight.

Typically, chickens begin their reproductive development after sensing an increase in day length, Bedecarrats said.

"Producers start by exposing chickens to eight hours, and will move on to 10, 12 and the ideal amount of time is 14 hours of light," he said.

As the amount of light exposure increases, a red wavelength is absorbed by a portion of the brain called the hypothalamus, which secretes hormones and controls sexual maturation.

In chickens that can see, different wavelengths usually blue and green stimulate receptors in the retinas, inhibiting reproduction, he said.

Blind chickens that lack retinas don't respond to the wavelengths that hinder reproduction, but they continue to be affected by the red wavelength.

While the research is still in its initial stages and could be a boon for egg farmers, Smoky Joes won't be the chosen strain for commercial production, Bedecarrats said.

"We are not really keeping these birds as producers in commercial farms, because any birds with genetic defects, whether it is blindness, or a physical defect, would never be used in farms," he said.

"These chickens only serve as models for our research, both on the commercial side and to get a better understanding of how biological processes in chickens work."