ABSTRACThe study investigated the effect of dietary protein levels on growth performance and body composition of the Nile tilapia, Oreochromis niloticus fingerlings (8.0 g), using a recirculating water system. The system consisted of eight rearing concrete tanks, underground plastic tank acts as a clarifier and upper plastic tank acts as a biofilter. The system was supplied with air and water pumps. Fish were fed on four dietary protein levels (20%, 25%, 30% and 35%) to satiaty for 6 days a week for 6 months. Results showed that fish growth was significantly affected by protein level. Fish fed on 30% protein diet attained the highest growth (higher weight gain, higher daily weight gain and higher specific growth rate). The best food conversion ratio (FCR) (2.05) was obtained by 30% protein diet, while the poorest FCR (2.72) was obtained by 20% protein diet. Protein efficiency ratio (PER) was significantly affected by protein levels. It decreased with increasing protein level. Results of body composition showed that protein and lipid contents were significantly affected by protein level. Protein content was significantly increased with increasing protein level in the diet. In contrast, lipid content was inversely affected by increasing the dietary protein level. The study showed that the recirculating water system is suitable for Nile tilapia culture in Egypt, and that a diet containing 30% crude protein is economical and suitable for Nile tilapia fingerlings feeding.

The present study was carried out at a private fish farm at Tolombat 7 site Kafr El-Sheikh Governorate, Egypt. The study was performed for 140 days during the period from 5 Th July to 27 Th November 2010. The study aimed to investigate the effect of different fertilization and feeding systems on growth performance; feed and Nitrogen utilization; whole body chemical composition; water quality; plankton abundance; some blood parameters and economic evaluation of earthen ponds cultured with different fish species in polyculture system. The experimental ponds were stocked with 4000 Nile tilapia (O. niloticus) fingerlings with an average initial weight of 17.18g; 500 Common carp (C. carpio) fingerlings initial weight of 16.50g; 750 Bouri (Mugil cephalus) fingerlings initial weight of 21.43 g; and 750 Tobara (Liza ramada) fingerlings with initial weight of 15.9 g in ten earthen ponds with dimentions of 21 x 100 m. each i.e. 1/2 fadden. Five treatments with two replicates each, were applied as follows: The 1 st treatment (T1) was fed only on a commercial fish feed (25% protein), where the daily allowance of the fish was calculated as 3 % of fish biomass/day for 6 days a week. The 2 nd treatment (T2) ponds were fed on the same artificial feed and fertilized with poultry manure at a rate of 32.5 kg /pond weekly. The 3 rd treatment (T3) was fed on the artificial feed and fertilized with poultry manure (32.5 kg /pond weekly) and 1 kg urea plus 4 kg triple super phosphate /pond weekly. The 4 th treatment (T4) received the artificial feed and fertilized with 1 kg urea plus 4 kg triple super phosphate/pond weekly. The 5 th treatment (T5) was fertilized by poultry manure 32.5 kg and 1 kg urea plus 4 kg triple super phosphate /pond weekly without artificial feeds. Results revealed that the highest (P<0.05) final weights and length, weight gain, length gain, daily weight gain, specific growth rate, relative growth rate and gross yield were recorded with T3 in all tested fish species compared to the other treatments, while T5 recorded the highest (P<0.05) condition factor in Nile tilapia, Common carp and Tobara and T2 recorded the highest (P<0.05) condition factor in Bouri. The best (lowest) feed conversion ratio was recorded with T4 followed by T3; T1 and T2, respectively, while T5 recorded no results of FCR, thus it received no artificial feed. Nitrogen utilization (N output/ N input) averages were 35.56; 32.18; 33.81; 35.90 and 116.40 for T1; T2; T3; T4 and T5, respectively. The applied treatments showed significant effects on whole fish body composition (protein, ether extracts, ash, NFE and gross body energy contents in all fish species tested. The treatment T3 recorded the highest total phytoplankton counts (org /ml) followed in a decreasing order by T2; T4; T5 and T1, respectively. The same trend was observed with total zooplankton and total plankton counts. The highest (P<0.05) total fish yield per pond was recorded by T3, followed in a significant decreasing order by T 2; T4 ; T1 and T5, respectively. The economical study...

A n experiment was conducted on 16 floating cages, each of a total water volume of lm 3 stocked with Nile tilapia ftngerlings weighing 30.67 to 30.22 g at the experimental start.The 16 cages represented four stocking densities (80 Dl; 100 D2; 120 »3 and 140 D4 fiih/m 3 ) and four protein levels within each density tested (PI 20 ; P2 24 ; P3 28 and P4 32%). The experiment lasted 6 months after start. Results obtained are summarized in the following: (1) Increasing the protein level within each stocking density increased significantly (P<0.05) both body weights and length of fish. (2) Wilhin each protein level tested, increasing the stocking demky resulted in significant decreases in body weight and length of Nile tilapia (3) Both protein levels and stocking densities released significant effects on gains in live weights, specific growth rate, feed conversion ratio and protein efficiency ratio. The total cage yield differed among the 96 Nabil F. Abdet-Hakim and El-Saied T. Moustafa where fish at a density of 120 fish/m 3 fed on the diet with 32% protein gave the highest yield of marketable size fish,

Effect of fresh or dried garlic as a natural feed supplement on growth performance and nutrients utilization of the Nile Tilapia (Oreochromis niloticas

An experimental study was conducted to evaluate the effect of three different natural growth promoters as feed additives on growth performance of monosex Nile tilapia fingerlings. Three nutritional treatments were applied at two additive levels (0.15 & 0.3 %) of Paprika (Hot Red Pepper "Capsicum annuum" meal), Proplis (Bee Glue) and Humapol-FIS Substance (Humic & Fulvic acids with Mixture of Minerals) each one in addition to Control diet. The tested treatments were conducted in two cement ponds (8×4×1 m), divided with nets to 16 equal aquatic compartments (2×2×1 m); 14 of them were used and stocked randomly with 20 fish/each one with an average initial body weight of 23.62 ± 0.13 g. The experiment lasted for 20 weeks (Six feeding days/week with the feeding rate at 3% of live body weight/day). The results at the end of the experiment showed that, growth performance and feed conversion ratio were significantly (P< 0.05) improved for monosex tilapia fingerlings fed on diets with the aforementioned natural feed additives compared to fish fed on the control diet. Feed cost required to produce 1kg weight gain compared to fish fed on the control diet was reduced by using the feed additives. These results revealed that using Proplis (P) at a dietary additive level of 0.3 % was the best treatment in terms of growth performance and feed utilization, while the highest revenue and the best economic evaluation were obtained from the Paprika (K) diet at a level of 0.3 % compared to the control diet.