Estimation of essential fatty acid requirements of common carp larvae using semi-purified artificial diets.

Two trials were conducted with duplicate groups of (first feeding) carp larvae fed artificial dry diets based on casein and dextrin over 21 or 25 days. One control diet based on yeast was also tested. Survival, growth and fatty acid profiles of larvae were studied. In trial 1, (n-3) fatty acid requirement was estimated using diets supplemented or not with methyl linolenate or cod liver oil. After 21 days, the best survival and growth were observed in larvae fed the unsupplemented diet [(n-3) fatty acid level: 0.05%]. Survival and growth were not improved by higher levels of (n-3) fatty acids. In trial 2, (n-6) fatty acid requirement was estimated using diets with graded levels of methyl linolenate or peanut oil. After 25 days, the best survival and growth were obtained with diets supplemented with 0.25% methyl linolenate (total (n-6) fatty acid level: 1%) or with 1.25% peanut oil (total (n-6) fatty acid level: 0.89%). Survival and growth were not improved by higher levels of (n-6) fatty acids. Fatty acid composition of carp reflected that of the diets and also showed that carp larvae are capable of elongating and desaturating linolenic acid and linoleic acid in longer chain fatty acids.