الفهرس 
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Abstract
This study was carried out during the period from the 1st of August 2004 till the 21fil of March 2005 at the hatching sale of the Integrated Fish Farm at Al Manzalah (General Authority for Fish Wealth Development - Ministry of Agriculture) in cooperation with the Department of Animal Production, Faculty of Agriculture, Al-Mansoura University. The aims of this study were to overcome the problems of overwintering Nile tilapia fish on their growth and reproduction, since this fish species is very sensitive for cold, which is a great problem for the Egyptian hatcheries. Therefore, lipids (fish oil, sunflower oil, and their mixture) as sources for energy and essential fatty acids (poly unsaturated) and vitamins (C and E) which support the immune system, stimulate the fertility and have ant oxidative properties were supplemented to the tilapia brood stocks’ diet during winter season aiming to improve the reproductive performance during the spawning season. Also, one of the commercial products (which took a great and false propaganda that it enhances immune system, prevents bacterial invasion, antistress, and improves the growth performance; namely Bio-Buds-2X) was used (for its inclusion of yeast, minerals, vitamins and enzymes) as feed additive in the overwintering fingerlings’ diet aiming to increase their survival and growth.