Effects of different dietary lipid sources on growth performance and tissue fatty acid composition of juvenile swimming crab Portunus trituberculatus

This study was conducted to evaluate the effects of dietary lipid sources on the growth performance and fatty acid composition of the swimming crab, P ortunus trituberculatus. Four isonitrogenous and isoenergetic experimental diets were formulated to contain four separate lipid sources, including fish, soybean, rapeseed, and linseed oils(FO, SO, RO, and LO, respectively). With three replicates of 18 crabs each for each diet, crabs(initial body weight, 17.00 ±0.09 g) were fed twice daily for 8 weeks. There were no significant differences among these groups in terms of weight gain, specific growth rate, and hepatosomatic index. However, the RO groups' survival rate was significantly lower than FO groups. The feed conversion and protein efficiency ratios of RO groups were poorer than other groups. The proximate compositions of whole body and hepatopancreas were significantly affected by these dietary treatments. Tissue fatty acid composition mainly reflected dietary fatty acid compositions. Crabs fed FO diets exhibited significantly higher arachidonic, eicosapentaenoic, and docosahexaenoic acid contents in muscle and hepatopancreas compared with VO crabs. Linoleic, oleic, and linolenic acids in muscle and hepatopancreas were the highest in the SO, RO, and LO groups, respectively. The present study suggested that SO and LO could substitute for FO in fishmeal-based diets for swimming crabs, without affecting growth performance and survival.

Growth Response and Fatty Acid Composition of Juvenile Procambarus clarkii Fed Different Sources of Dietary Lipid

An experiment was conducted to evaluate the effects of feeding various sources of dietary lipid on weight gain, feed conversion, survival and fatty acid composition of juvenile red swamp crawfish, Procam-barus clarkii. Six semi-purified diets containing vitamin-free casein, defatted soybean meal, 0. 5% choline chloride, 0. 5% glycine and 0. 5% cholesterol were supplemented with 6. 0% of either anchovy oil, linseed oil, soybean oil, rapeseed oil, safflower oil or pork lard. Each diet was fed to crawfish (3. 07±0. 21 g average weight) in three replicate aquaria for 60 days. Survival rate, weight gain and feed conversion were best for crawfish fed the diet containing anchovy oil. Crawfish fed the linseed oil diet had the second highest weight gain, followed by crawfish on soybean oil, repaseed oil, safflower oil and pork lard diets, respectively. Feed conversion values were a reflection of weight gain. Results showed that both n-6 and n-3 fatty acids are dietary essential for juvenile Procambarus clarkii, although n-3 fatty acids promoted faster growth than n-6. However, highly unsaturated fatty acids (HUFA) (20 : 5n-3 and 22 :6n-3) had better growth-promoting effect than 18 : 3n-3, due probably to the limited ability of crawfish to bioconvert fatty acids to polyenoic forms of longer chain length. The fatty acid composition of the crawfish generally reflected that of the dietary lipids, especially for the diets containing unsaturated fatty acids.