Abstract
Lighting system is a stimulant for reproduction in some species (Horses) and an inhibitor for others (Sheep). This study started on September 1st and planned to study the effects of different lighting regimes and melatonin treatment on the receptivity and performance of 78 (60-does and 18-bucks) New Zealand White rabbits, which were reared in a private Rabbitary in Menuofia Governorate, Egypt. These rabbits were randomly assigned to six treatment groups of 10 does and three bucks for each (8, 10, 12, 14 and 16 hours light (HL) and melatonin- treated). Ejaculate traits, sexual activity of bucks, sexual receptivity and reproductive performance of does were recorded. Results revealed that exposure of rabbits to long photoperiods (14 and 16HL) or treatment with melatonin improved the quantity and quality of ejaculate traits and buck sexual activity. Moreover, does sexual receptivity, feed intake, litter size and weight at birth and weaning were increased by long photoperiods (14 and 16HL) or treatment with melatonin. On the other hand, gestation period and pre-weaning mortality rate were decreased. It can be concluded that application of long photoperiods is beneficial to rabbit producers and 14 HL : 10 hours dark is optimal for satisfying the biological requirements of the rabbits. Finally, the light schedules can be used for biostimulation instead of melatonin.

Key words: Light schedules, Melatonin, New Zealand White rabbits, Sexual receptivity.