الفهرس 
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Abstract
This study was carried out at the Research Station for duck at EL-Serw ofanimal production Research institute, Agriculture Research Center. Domiaty duckling were used in the study. At 18 weeks of age birds kept under 4 lightintensity treatments to be L I.5, L10, L45 and L90 Lux provided by incandescentbulbs, 10, 40, 100 and 200 watts and all birds were exposed to 17 hourslight/day by using artificial light supplemented to natural day light to be onehour in early morning before sunrise and the rest was added at the sunset. Birdswere housed in two different sex ratios, 4male:1female or 6 female:1male. The total number of ducks used in this experiment was 456 females and 96drakes (first experiment), in addition to 80 female and 24 drakes (secondexperiment) were used. Birds were fed ad-libitum, a starter (0-6 weeks), agrower (6-18 weeks)and a layer diets (18-60 weeks).This study aimed to investigate the effects of intensity of supplementarylight, sex ratio and laying period on some reproductive traits and bloodconstituents.The obtained results show that:The increasing the intensity of supplementary light for the flock of Domiaty duck breeders during the laying season to 10 Lux had in generalconsiderably positive effects on their reproductive performance. In addition, males were positively responded also by producing semen of better quality during the laying season and hence maintaining the good fertility of theproduced eggs.The number of females per each drake can be increased from 4 to 6 forobtaining good reproductive performance and then save about 9-10% of thedrakes required for natural mating.