IJA Volume 54, Issue 2, 2002
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ItemThe Protein Sparing Effects Of High Lipid Levels In Diets For Rainbow Trout (Oncorhynchus Mykiss, W. 1792) With Special Reference To Reduction Of Total Nitrogen Excretion(Israeli Journal of Aquaculture - BAMIGDEH, 2002)This research sought to develop low-protein, high-energy (less-polluting) diets for rainbow trout to properly utilize protein and reduce total nitrogen excretion. Duplicate groups of rainbow trout were fed one of four experimental diets with a protein to energy (P:E) ratio of 25, 24, 22 or 19 mg/kJ and a lipid content of 12, 13, 17 or 26%, respectively. The diets were given to fish with a mean initial weight of 181 g for 70 days. At the conclusion of the trial, mean weights ranged from 353.17 g (94% weight gain) to 394.75 g (118% weight gain) with 100% survival in all treat- ments. Weight gain, feed efficiency and protein retention increased as the dietary lipid content increased and as the P:E ratio decreased. Fish fed the 22 mg protein/kJ energy diet (17% lipid, 44% protein, 20.34 kJ/g gross energy) performed best. This indicates that the protein content in practical trout feeds can be reduced from the currently used 47% to around 44% without reduc- ing the growth rate and feed efficiency, if high quality protein is used and the gross energy is increased by lipid to about 20.34 kJ/g diet. The low-protein, high-energy diets reduced the total nitrogen excretion from the rainbow trout by 27%.
ItemEarly Development And Growth Of Arctic Charr (Salvelinus Alpinus) And Rainbow Trout (Oncorhynchus Mykiss) At A Low Water Temperature(Israeli Journal of Aquaculture - BAMIGDEH, 2002)Hatchery traits and growth of eggs and fry of rainbow trout, Oncorhynchus mykiss, and arctic charr, Salvelinus alpinus, were tested in fresh water of a low temperature. There were significant differences (p<0.05) between the survival rates from fertilization through the eyed stage and the first exogenous feeding. No significant differences were observed between species with regard to feed conversion or survival of fry at the end of the 154-day trial, but weight gain and specific growth rate differed significantly (p<0.05). These results suggest that the arctic charr could be considered an alternative to rainbow trout, particularly in coldwater farms.
ItemMicroflora On The Skin Of European Eel (Anguilla Anguilla L., 1758) Sampled From Creek Yuvarlakçay, Turkey(Israeli Journal of Aquaculture - BAMIGDEH, 2002)Bacterial skin microflora of eel obtained from Mugla (Turkey) province were studied. The aero- bic bacteria associated with skin and slime were estimated using the dilution plate technique. The dominant bacterial species were Pseudomonas spp. (17.23%), Acinetobacter baumannii (15.51%) and Stenotrophomonas maltophilia (12.05%). A lower frequency of Gram-positive bacteria (18.93%) was found in samples.
ItemInfluences Of Dietary Protein Deficiency On Amino Acid And Fatty Acid Composition In Tilapia, Oreochromis Niloticus, Fingerlings(Israeli Journal of Aquaculture - BAMIGDEH, 2002)The influence of dietary protein deficiency on the amino acid and fatty acid compositions of tilapia (Oreochromis niloticus) fingerlings was studied. Two experimental diets (0.81% and 33.32% protein, dry matter) were prepared. The protein content of fish fed diet 1 (0.81% pro- tein) decreased from 57.14% to 49.18% in eight weeks. Fish fed diet 2 (33.32% protein) had higher protein and amino acid contents. The lipid content of fish fed diet 1 was higher than that of fish fed diet 2, suggesting that carbohydrates transformed into lipids. The levels of fatty acids 16:0 and 18:2 n-6 in fish fed diet 1 remained nearly unchanged and did not reflect the diet, demonstrating that fatty acids in diet 1 may not have been incorporated into the triglycerides of the tissues. Possible impairment of lipid secretion from the liver, caused by depletion of protein in the blood lipoprotein, may have affected the transport of lipids to the muscles. A dietary pro- tein deficiency results not only in a deficiency of essential amino acids in the body but also affects transport and storage of lipids within the fish.