THE EFFECT OF DIFFERENT RATIOS OF N-6/N-3 FATTY ACIDS IN BROODSTOCK DIETS ON EGG QUALITY OF CATFISH, CLARIAS BATRACHUS.
I. Mokoginta, T. Takeuchi, D.S. Moeljohardjo, K. Sumawidjaja, D. Fardiaz-1998
Asian Fisheries Science, 11: 157-168
Abstract:
This experiment was conducted to acquire biochemical information on the quality of catfish eggs in relation to different n-6/n-3 ratios of fatty acids in the broodstock diet. Five experimental diets, which were isonitrogenous and isoenergy, but containing different levels of n-6 and n-3 fatty acids (diet A: essential fatty acid (EFA)-deficient diet containing 0.21% n-6 fatty acid. 0.03% n-3 fatty acid; diet B: 0.67%, 2.09%; diet C: 2.24%, 0.07%; Diet D: 1.85%, 0.56% and diet E: 0.26%, 1.68%) were used in the experiment. Five-month-old fish were fed the experimental diets for 10 months. Samples of the eggs produced by the respective broodstock were fertilized by the sperms. Samples of eggs during embryogenesis were analyzed for total lipid (TL), polar lipid (PL) and nonpolar lipid (NL) content as well as fatty acid (FA) composition. The hatching rate of the eggs and the percentage of abnormal larvae were determined. Results showed that the lipid content of the eggs decreased from the first hour after fertilization. The lipid content of the EPA-deficient eggs (diet A) and the n-3 fatty acid deficient eggs (diet C) decreased significantly during embryogenesis compared to the lipid content of the eggs of other diets. Also, in general, the NL of eggs was much lower than PL during embryogenesis. The NL of diet A and diet C eggs was also much lower than PL during embryogenesis compared to the NL of the eggs from the other diets. The n-6 and n-3 fatty acid levels of unfertilized eggs were influenced by the fatty acid level in the broodstock diet. The n-6 and n-3 fatty acids of NL were much lower than those of PL, especially in the organogenesis stage of the larvae. The n-6 and n-3 fatty acids of NL, from diets A, B and C were also much lower compared to those of diets D and E. Hatching rates of eggs produced by the broodstock fed diets and D and E were also higher than those fed diets A, B and C.
(Faculty of Fisheries, Bogor Agricultural University, Kampus IPB Darmaga, Bogor 16680, Indonesia)