In this experiment, a total number of 165 birds (150 female + 15 male) from each developed laying hens Silver Montaza and Matrouh 20 weeks old up to 40 weeks of age. All bids were weighted and randomly distributed into five treatments with three replicates per treatment (10 females and 1 male / replicate) with almost similar initial average body weight. Feed and fresh water were ad libitum during the experimental period. Each experimental group was exposed to natural day light and supplemented with Ultraviolet light as in its program light, the first group (control group) exposed to no UV light, the second, third, fourth and fifth groups were exposed to 1, 2, 3 and 4 hours/day respectively to UV light from UV lamps after sunset, and controlled by a timer as following :
1- Hens in the first treatment were exposed to sun light and yellow lamps to 17h/day without exposed to UV lamps (Control).
2- Hens in the second treatment were exposed to sun light to sunset, UV lamps for 1h/day and supplemented with yellow lamps to the end of light period.
3- Hens in the third treatment were exposed to sun light to sunset, UV lamps for 2h/day and supplemented with yellow lamps to the end of light period.
4- Hens in the fourth treatment were exposed to sun light to sunset, UV lamps for 3h/day and supplemented with yellow lamps to the end of light period.
5- Hens in the fifth treatment were exposed to sun light to sunset and UV lamps for 4h/day without exposed to yellow lamps. Birds were reared under similar condition.
The results indicated that live body weight (LBW), feed intake (FI), egg mass, some blood components, immune responses to sheep red blood cells and New castle were significantly improved (P≤0.05) by exposed birds to UV lamps after sunset supplemented in its program light. It could be concluded that the efficient exposed time to UV lamps was (2-3 hours/day) for silver Montaza and Matrouh developed laying hens.