الفهرس 
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Abstract
The water fowls, ducks and geese were along the river Nile in the valley and delta in Egypt, since the Ancient Egyptains (5000thousands year B.C.).The Present work aimes to :Throw some light on the effect of the different combinations of light dark systems of normal and abmormal lengths (ahemeral - non 24 his) on events of egg lay of pekin ducks. The traits studies were rate of lay, oviposition rythm, egg laid in 8 hrs model, egg cluch, paues lengths, egg and its components weights, fertility and plasma steroid hormones during the ovulatory cycle.