July 19, 2007

Research finds blind chickens start reproduction earlier

A researcher from the University of Guelph has found that a naturally blind species of chickens not only begins reproduction earlier but also lays more eggs.

Currently the research is focusing on how this is so. The research would shed more light on how producers can use light techniques for higher performance.

Gregoy Bedecarrats, Animal and Poultry Science, is studying how light affects reproduction patterns in a flock of blind Smokey Joes, a strain of White Leghorn birds,

According to Bedecarrats, chickens typically start reproductive development after sensing an increase in day length, when more light is absorbed by a portion of the brain - the hypothalamus.

However, in blind chickens, light is being integrated differently. Although light directly stimulates the hypothalamus, it also inhibits reproduction when it is perceived by the retina of the eye.

Since blind birds lack retinas, they experience only the stimulatory influence on the hypothalamus, which encourages them to begin laying eggs earlier.

Bedecarrats said there are two pathways 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 stimulates 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. On short days, the inhibitory pathway is prevalent; on long days, the red rays overpower and initiate reproductive maturation.

Since blind birds lack retinas and therefore do not have the inhibitory effects of the blue-green rays, so they begin laying eggs earlier, even without any increase in day length.