Birds have two photoreceptors, one retinal receptor, the eye, and the other in the hypothalamus. The stimulation of light reaches the hypothalamus through the nerves of the optic nerve lobe; In addition, light can also act directly on the pineal gland and hypothalamus through the skull. The hypothalamus is stimulated to secrete gonadotropin-releasing hormone, which travels through the pituitary portal system to the anterior pituitary gland, causing the secretion of follicle-stimulating hormone and ovulatory hormone, which promotes the development of follicles and ovulation. The developing follicles produce estrogen, which promotes the development of the fallopian tubes and the manifestation of secondary sex characteristics in the hen. Ovulation hormones cause ovulation in the hen.
In the production of commercial laying hens, artificial light is often used to supplement the lack of natural light, or only artificial light is used to reasonably adjust the light required by laying hens. Suitable light can increase the egg production of laying hens, accelerate the weight gain rate of broilers, strengthen blood circulation and appetite of chicks, help calcium and phosphorus metabolism, and enhance immunity.
