Effects of dietary lipid levels on growth,nutrient digestibility and body composition of Chelon haematocheilus

In order to determine the optimal demand of lipid for Chelon haematocheilus,the effects of various levels of fish oil added to diets on growth,apparent digestibility coefficients and body composition of Chelon haematocheilus.Three hundred and sixty Chelon haematocheilus fingerlings with initial body weights of(5.4±0.2) g were randomly divided into 3 groups(3 duplicates for each group,and 20 fish in one duplicate).The fish were fed diets with six levels of crude lipid at 2.71%,5.79%,8.23%,11.85%,14.39% and 16.91% by adding 0,3%,6%,9%,12% and 15% fish oil.The results showed that the hepatosomatic indexes of 14.39% group and 16.91% group were significantly higher than that of other four groups(P0.05),and there was no significant difference in other four groups(P0.05).The weight gain rate and special growth ratio firstly increased and lately decreased with increased dietary lipid levels.The highest weight gain was found in the 8.23% group,and the lowest feed conversion ratio also appeared in the 8.23% group.Protein efficiency ratio increased with increased dietary lipid levels.Protein efficiency ratio of the 16.91% group was significantly higher than that of 2.71% group and 5.79% group(P0.05),and there was no significant difference in other groups(P0.05).Dietary lipid levels had no significant effects on the digestibility of dry matter and crude protein(P0.05).With the increase of dietary lipid levels,the apparent digestibility of the 16.91% group was significantly higher than that of 2.71% group(P0.05),the lipid content of whole body rose,with the 14.39% group and 16.91% group significantly higher than the 2.71% group(P0.05).There was no significant difference of muscle lipid content in other four groups(P0.05).It was concluded that dietary lipid levels affected partial body indexes as well,especially the hepatosomatic index;the digestion of crude fat was improved by the addition of lipid in diet,and excessive lipid in diet made the whole body fat deposition increase and the muscle moisture and crude protein decrease.Based on second-order polynomial analysis,the optimal lipid demand was spike level of 9.30%-9.64% for Chelon haematocheilus.