OAC prof explores how light affects reproduction in naturally blind chickens
A strain of chickens that are naturally blind start reproduction earlier and produce more eggs per cycle than their sighted counterparts, a U of G researcher has found. Now he’s working to understand what influences the increased production in blind birds.
Prof. Grégoy Bédécarrats, Animal and Poultry Science, has been studying how light affects reproduction patterns in a flock of blind Smokey Joes, a strain of White Leghorn birds. He says better understanding of how light influences reproduction in birds will give producers more tools to alter light techniques for higher performance.
�We’re at the early stage, but this research will be very beneficial to producers as a management tool,� Bédécarrats says.
This study began in 2004 when he was given a flock of blind Smokey Joes by researchers from Michigan State University. At that point, few studies had been done with the birds, and he was eager to learn more.
Typically, chickens start reproductive development after sensing an increase in day length, says 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. In blind chickens, however, he learned that light was being integrated differently.
In the study, he found that although light directly stimulates the hypothalamus, it also inhibits reproduction when it is perceived by the retina of the eye. Because blind birds lack retinas, they experience only the stimulatory influence on the hypothalamus, which encourages them to begin laying eggs earlier.
Bédécarrats says two different pathways co-exist in birds to interpret their daily exposure to light. The first is a pathway that involves blue-green light wavelengths (mainly perceived by the retina). The second pathway involves wavelengths from the red spectrum, which penetrate the skull and stimulate the hypothalamus.
He suggests that blue-green rays can have inhibitory properties and that red rays are what stimulate chickens to begin their laying cycle. When both pathways co-exist (in normally sighted birds), the amount of light they’re exposed to each day dictates the physiological response. So on short days, the inhibitory pathway is prevalent; on long days, the red rays overpower and initiate reproductive maturation.
Because blind birds lack retinas, they don’t have the inhibitory effects of the blue-green rays, so they begin laying eggs earlier, even without any increase in day length, says Bédécarrats. Now he hopes to further explore when and how the retina degenerates in blind chickens.
Some of the chicks in the blind strain are born with sight but lose it within the first three weeks. Blind birds are less aggressive and less stressed from human interaction, he says.
Working with the genetically blind chickens provided some challenges that required alterations in the animals’ housing, including the installation of hard drinking cups in place of nipple drinkers so the birds could identify the cups more easily. Bédécarrats says the blind chickens adapted better when they had sighted birds to follow so they could map the environment.
Although five forms of hereditary retinal degeneration have been previously reported in chicken strains such as Rhode Island Red and White Leghorn, research has focused on mapping genes that could be used to advance the human medical field. Bédécarrats says more research is needed to determine how blind birds can be used to benefit the poultry industry.
Also involved in this project are graduate students Jennifer Perttula and Heather
RESOURCE: News @ Guelph
BY PATRICIA DICKENSON
POSTED: June 20, 2007