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The reproductive performance of roosters improves according to the changes in the lighting color

From a study at the Hebrew University it becomes clear that artificial lighting plays a central role in the reproductive processes of poultry. Prolonged exposure to light in a red wave absorbed through the extraretinal receptors while suppressing the activation of retinal photoreceptors has a positive effect on the reproductive capacity of chickens. The study was published in the journal Poultry Science.

The effect of the types of lighting on the reproductive systems of chickens. The image was prepared by DALEE and is not a scientific image
The effect of the types of lighting on the reproductive systems of chickens. The image was prepared by DALEE and is not a scientific image

Birds perceive and process light in two different and separate ways: through photoreceptors in the retina of the eye and extraretinal photoreceptors located in the brain without passing through the retina at all. Through the retina of the roosters light is mainly absorbed in a green wave and through the extra-retinal receptors mainly light in a red wave is absorbed.

A new study led by Prof. Israel (Roli) Rosenbaum and Master's student Ms. Yoana Bertman, from the Department of Animal Sciences in the Faculty of Agriculture, Food and Environment at the Hebrew University, found unexpected consequences for changes in the absorption of light in roosters - it turns out that artificial lighting plays a central role in the reproduction processes of poultry . Prolonged exposure to light in a red wave absorbed through the extraretinal receptors while suppressing the activation of retinal photoreceptors has a positive effect on the reproductive capacity of chickens. The study was published in the journal Poultry Science.

Prof. Rosenbaum explains the reason why he decided to examine the issue: "It started when I was on sabbatical in the United States several years ago, so I focused on research on turkeys. Regardless of the research I was doing at the time, I came across studies from the fifties of the last century that were conducted on chickens (females) and showed a surprising correlation between the eyesight of different birds and reproduction. The birds with retinal vision impairment (blindness) were more fertile and laid more eggs." The discovery prompted Prof. Rosenbaum to investigate why this happens and how it is possible to control the effect of different types of exposure to light on reproduction in poultry, males and females. This is the first time ever that the effect of vision on reproduction has been tested in male roosters.

In order to test the issue, roosters at the age of 21 weeks were housed in five light-controlled coops in individual cages. Two lighting systems were installed in the chicken coops: red, which is absorbed through the brain, and green, which is absorbed through the eye. Until the age of 24 weeks, before sexual maturity, the roosters were exposed to 8 hours of lighting in both colors at the same time. Upon reaching the appropriate age, the researchers "extended" the roosters' day gradually up to 14 hours by extending only the red light, and the green light remained on a short day. Thus, the brain of the roosters received longer stimulation while the eye is still on a short day. Once a week the quality of the semen of the roosters was tested and once a month blood tests were taken and selected glands were taken for genomic examination. The experiment was conducted until the age of 65 weeks.

The results of the experiment showed that precise lighting improves the performance of heavy breeding (for broiler purposes and not for eggs). The roosters that underwent activation of the brain photoreceptors with red light and at the same time the activation of the retina was suppressed by giving a short green day showed at the age of 65 weeks a significant increase in the weight of the testicle and the volume of the seminal fluid and an improvement in motility. The results were also proven valid in a field experiment in commercial chicken coops.

Yoana Bertman, a master's student in Prof. Rosenbaum's laboratory who led the research, explained the results: "We found that stimulation of extracerebral photoreceptors increases reproductive activity, while stimulation of the retina suppresses it. The activation of the retina of the roosters causes the production of serotonin in the birds, which suppresses reproduction. Even when we did not manipulate the lighting in the chicken coops, but inhibited the production of serotonin in the roosters, we saw a significant improvement in reproductive performance and hormonal and genomic indices."

for the scientific article

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