Nutritional and environmental toxicological investigations on fish farms in Fayoum governorate, Egypt

This study was carried out in two fish farms in EL-Fayoum Governorate to investigate water quality, evaluate the effect of chemical fertilizers and artificial diet on the performance and feed efficiency of Oreochromis niloticus and Mugil cephalus, and determine pesticide residues in water and reared fish. Average values of water temperature in fish farms and water source ranged between 25.6 and 30.6°C. The highest values of dissolved oxygen were observed during April while the lowest values were found in June and July. There was a negative relationship between water temperature and dissolved oxygen, a positive relationship was found between temperature and water salinity. The highest values of weight gain [270.90, 269.20g], specific growth rate [1.15, 1.16], feed consumption [240.60, 270.48g] and feed conversion ratio [0.89, 1.01] of O. niloticus and M. cephalus, respectively were found in fish fed on artificial feed and reared in fertilized ponds when compared to fish fed on artificial diet only or reared in fertilized ponds without supplementary feed. The pesticide residues of chlorpyrifos ethyl and fenpropathrin were detected in water at mean levels ranged 0.10 - 0.25 mg/I. Both fish species contained fenitrothion residues at values [0.525 mg/ kg and 0.255 mg/kg for O. niloticus and M. cephalus, respectively] which are higher than permissible limits. Although the residues of fenitrothion and carbaryl were not detected in water, they were found in both fish species which could be attributed to the ability of these pesticides to bioacumulate in the aquatic organisms

Digestibility determination in nile catfish fingerlings using internal and external markers

Digestibility trials were conducted to compare the use of one external dietary marker [chromic oxide] and two natural internal dietary markers [crude fiber and acid insoluble ash] for the estimation of apparent protein and energy digestibility in catfish, Clarias lazera. The fecal samples were collected daily by filtering the water and from the stomach and the rectum at the end of each trial. From the results obtained, it was concluded that chromic oxide [0.5%] can be considered as the most suitable "foreign" dietary marker, while acid-insoluble ash was found to be suitable good internal marker, particularly under practical farming conditions

Digestibility of fish silage and fish meal by nile tilapia [oreochromis niioticus]

Two digestibility trials were conducted. The first trial determined the digestibility coefficients of the local fish meal [low quality], fish meal [medium quality], fish silage made from fish processing waste and fish silage made from unusable fish for human consumption which were fed as single ingredients for 5 days. The apparent digestibility coefficient of protein, lipid, calcium and phosphorus were higher for the fish silage [which was made from unusable fish for human consumption] followed by the other fish products. The second trial determined the digestibility coefficient of four diets, whereas, each diet contained one source of fish silage made from unusable fish for human consumption and fish silage made from fish processing waste. The present data also indicated that the nutritional value of fish silage was improved by storing the ingredients at -5C prior to ensiling, and the diets done using these silages contained more intact protein and less free amino acids than diets done using conventional fish products