Effect of protein sources on disease resistance factors and growth performance of Nile Tilapia [Oreochromis niloticus]

Four groups of Nile tilapia [oreochromis niloticus] each contain 30 fish were fed four approximately isonitrogenous and isoenergetic diets formulated with different protein sources. The growth performance were studied during the period of 120 days. After this time, 10 fishes from each group were immunized with Aeromonas hydrophila bacterin and the remainder fish [20 fish] were exposed to artificial infection with A. hidrophila by immersion method. The antibody titres were detected weekly by agglutination test while the mortalities percent were recorded throughout 15 days post challenge. The growth performance including weight gain [WG] percent, specific growth rate [SGR], food conversion ratio [FCR], protein efficiency ratio [PER] and protein retention were higher in fish fed the diet containing fish meal than bone and meat meal, cottonseed meal and sunflower meal. There was a significant different [P < 0.05] between fish meal diet and all experimental diets in most studied criteria. Fish fed diets containing protein of animal sources [fish meal and meat and bone meal] responded to immunization with production of specific antibodies more than the fish fed diets containing protein of plant sources [cottonseed meal and sunflower meal]. The mortalities percent resulting from artificial infection with A. hydrophila were 20, 25, 35 and 35 in groups fed diets containing fish meal, bone and meat meal, and sunflower meal respectively

Studies on Nile tilapia [Oreochromis niloticus] male production and their susceptibility to bacterial and fungal infections

Nile tilapia [0. niloticus] male production was established by feeding of 17 alpha methyltestosterone at various levels for different durations. Four months from hatching, the fish were sexed by dissection. The fish fed hormonal treated and untreated diets were exposed monthly, from hatching till 120 days of age, to artificial infection with Flexibacter columnaris and Saprolegnia diclin. All male production [100% male] was obtained from the group fed diet containing 30 micro g 17 alpha methyltes-tosterone/g diet for 21 days, while the male percentage in groups fed diets containing 45 and 15 micro g of hormone/g diet for 14 and 42 days were 68 and 56 respectively. The male percent in the control group was 52%. The mortality ratio of artificial infection with F. columnaris and S.diclina in groups fed the hormonal treated and untreated diets were directly proportional with the male percent in each group. Since, the mortalities of F. columnaris and S. diclina infection in the group of all male production at 120 days of age were 40 and 42% respectively, followed by the mortalities in the group of 68% male which were 36 and 43% respectively. The mortality ratio in the control group [52% male] were 30 and 28% for the same organisms respectively and at the same time

outbreak of redmouth disease among cultured fresh water fishes in Ismailia governorate

A severe outreak of redmouth disease in a fish farm located at Ismailia governorate involved 30% and 40% mortality rates in both Oreochromis niloticus and Cyprinus carpio fishes. A total of 30 clinically diseased fishes were examined for the presence of the major causative pathogen. Aeromonas hydrophila was recoverted from all the examined cases. Intraperintoneal inoculation of A. hydrophila was carried out in 40 apparently healthy fish of both spieces and re-isolation of the pathogen was done after the clinical signs postmortem lesion were observed. Treatment of the diseased fish was carried out after using the disc diffusion technique with oxytetracycline which gave good results