Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Animal Production

Nile tilapia juveniles (Oreochromis niloticus L.) (24.8 g/fish) were subjected to four feeding regimes (32 fish per tank) that included three feed deprivation and re-feeding cycles for a duration of 84 days. Each feeding cycle constituted one treatment. The one day deprivation cycle included feed deprivation for one day followed by three days re-feeding period. The two-day deprivation cycle included feed deprivation for two days followed by six-day re-feeding period. The three-day deprivation cycle included feed deprivation for three days followed by nine-day of re-feeding period. All feed deprivation cycles were repeated all over the experimental period. The control treatment was fed to satiation every day without any period of feed deprivation. Nile tilapia was fed with commercial extruded diet (32% crude protein). Starting with initial weights of 24.4-25.2 g/fish at the start of the experiment , Nile tilapia grew to 55.0 -71.3 g /fish at harvest time, with significant differences in growth patterns among treatments (P<0.05). Fish within food deprivation treatment did not differ significantly in terms of final body weight which ranged from 55.0 to 63.02 g /fish (P<0.05). All fasting treatments had similar feed conversion ratio compared to the continuous feeding (control) group (P<0.05) which indicate that FCR in the food deprivation groups was compensated during re-feeding by a decrease in metabolic costs or an improvement in feed utilization. In practical situations fish should be deprived from feeding in case of high ammonia concentrations in fish ponds to avoid the risk of ammonia toxicity

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