Blind Chickens Lay More Eggs (7/23/2007)

A strain of chickens that are naturally blind produce more eggs than their sighted counterparts, a U of G animal scientist has found.

As part of his research into how light influences reproduction in birds, Prof. Grégoy Bédécarrats discovered that a genetically blind strain of White Leghorn birds called Smoky Joes start reproduction earlier and produce more eggs than the average chicken.

Bédécarrats began studying the reproduction patterns of these birds in 2004 to better understand how light influences the overall production of eggs. Understanding this will help producers develop lighting techniques that will achieve higher performance, he said.

"We're at the early stage, but this research will be very beneficial to producers as a management tool."

Typically, chickens start reproductive development after sensing an increase in day length, said Bédécarrats. This happens when more light is absorbed by a portion of the brain called the hypothalamus, which secretes hormones and controls the part of the nervous system responsible for regulating automatic body functions such as temperature, blood pressure, thirst, hunger and the sleep-wake cycle.

But he learned that light is integrated differently in blind chickens.

Bédécarrats found that although light directly stimulates the hypothalamus, it can also inhibit reproduction when it is perceived by the retina of the eye.

Because blind birds lack the retinas' response that inhibits reproduction, they experience only the stimulatory influence on the hypothalamus, which encourages them to begin laying eggs earlier, he said. In the male birds, he also found they reached sexual maturation quicker.

A colony of these birds, which were originally bred at Michigan State University, has now been established at U of G. Other breeds of chickens have mutations that cause retinal degeneration, but Bédécarrats said the prevalence of the condition appears to be elevated in this strain of White Leghorn, making it an ideal research model.

Although his current research is focused on increasing reproductive performance in domestic birds, he said his recent findings are also being used to develop ways of controlling the reproductive behaviour of other birds in captivity. He is currently working on a project in this area with Michael Taylor, a veterinarian at the Ontario Veterinary College.

Because companion and zoo birds live in controlled environments with dependable food sources, they tend to lay too many eggs and often develop severe health conditions as a result, he said.

"Results from this research could potentially lead to new therapeutic strategies for zoo and companion animals."

Note: This story has been adapted from a news release issued by the University of Guelph

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