ABSTRACThe present study was conducted to determine the dietary protein requirement for optimal growth performance and body composition of juvenile sole fish. Four diets were formulated with different protein levels (D40, D45, D50 and D55% crude protein). The silverside fish (Atherina boyeri) was added to the diets as local animal protein source and to enhance palatability of the test diets. Fish were fed the artificial diets as 2% of the fish biomass daily divided into two equal portions. Juvenile sole with an initial weight of (6.65±0.2g) were distributed as 40 juveniles in each triplicate tank, each of 1m 3 volume. The experimental period lasted 120 days after start. The results showed significant differences (P<0.05) in growth performance and feed efficiency between diets. The highest performances in terms of (Finial weight, Weight gain, Average daily gain, Specific growth rate, Condition factor, Feed conversion ratio, Protein efficiency ratio, Protein productive value and Hepatosomatic index) were obtained with the D55% CP, followed by D50%, without significance difference between them. However, fish fed D40% crude protein diet recorded less performance parameters. No significance difference (P<0.05) in whole body chemical composition (dry matter, crude protein, crude lipid and ash) were found between fish fed all experimental diets. However, slight increase in whole body lipid contents were recorded with D50%CP and D55%CP levels. The results of the present study indicated that, D55% crude protein level can be optimal for meeting the requirement of juvenile sole, Solea aegyptiaca without adverse effects on growth performance and feed efficiency.

An experiment of 90 days was performed to study the effect of two sublethal levels of copper (Cu) (0.25, 0.125 ppm), mercury (Hg) (0.01, 0.005 ppm), lead (Pb) (3, 1.5 ppm) and cadmium (Cd) (2, 1 ppm) on growth performance, body composition and residual concentration of the Nile tilapia (Oreochromis niloticus). A set of 324 fish with 17 g average initial weight were divided into 36 similar groups in glass aquaria containing 90 liter of water in each. Treatments and control were allocated to the experimental groups in triplicates (3 groups / treatment). The fish were fed on commercial diet containing about 30% crude protein at a rate of 3% of the body weight daily during the experimental period. The results showed that, Cu, Hg, Pb and Cd caused a significant reduction in average weight gain (AWG), specific growth rate (SGR), and survival rate (SR) of Nile tilapia at the two levels studied as compared with the control. Feed conversion ratio (FCR) and protein efficiency ratio (PER) were the worst in groups exposed to the high levels of the investigated 4 heavy metals. On the other hand, the sublethal levels of Cu, Hg, Pb and Cd decreased crude protein (CP), and increased ether extract (EE) and ash in the body of Nile tilapia. Residues of the investigated heavy metals were higher in fish groups treated with them and their concentrations increased with increasing the level of heavy metal. The highest level of residues was found in the liver and kidney of fish groups treated with the high level of the investigated heavy metals.

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The development of the activity of pancreas lipase was observed at lambs reared with and without ewes from their birth to an age of four weeks and in a second series between five and 18 weeks. A statistically significant influence of the age on the level of activity of pancreas lipase could be observed. It was also influenced by the feeding regime, that is, the lambs reared without ewes which were fed restrictively with milk replacer showed a significantly higher activity of pancreas lipase on comparison with lambs reared with milk replacer ad libitum or those reared by ewes. 8-week-old lambs after a suckling period of four weeks and the subsequent sole feeding with pelleted mixed feed reached approximately the same activity of pancreas lipase as adult wethers.

This work was carried out to study the effect of different sources of dietary antibiotics (Zinc bacitracin, Flavomycin, Virginiamycin) in rations with optimal protein levels (starter phase: 23.5%, finisher phase: 20.0%) and low protein levels (starter phase: 19.6%, finisher phase: 17.0%) on broiler performance with 8 groups of 75 broiler each. The supplement of diets, containing the optimal and low protein level, with antibiotics increased the body weight after 7 weeks of age and improved the feed conversion as compared with control groups. Virginiamycin was superior in increasing body weights after 7 weeks of age and in improving the feed conversion with rations containing low protein level when compared with zinc bacitracin and Flavomycin. When broiler rations, low in the protein content, were supplemented with antibiotics, they could not substitute the difference in optimal protein level. Antibiotics supplementation increased the value of improvement in production efficiency and this was more pronounced with Virginiamycin.