Effects of coated amino acids and protease supplementation in low fish meal diets on growth, nutrient utilization and digestive enzyme activities of white shrimp

Abstract:

This experiment was conducted to evaluate the effects of coated amino acids and exogenous protease supplementation in low fish meal diet on growth, nutrient utilization and digestive enzyme activities of white shrimp (Litopenaeus vannamei). A high fish meal diet (containing 20% fish meal) and a low fish meal diet (containing 15% fish meal) were designed as the positive and negative control diets respectively, and coated lysine (500 mg/kg), coated methionine (900 mg/kg) (CAA) and 175 mg/kg exogenous protease were supplemented in negative diet solely or combinedly to form another three experimental diets. The five isonitrogenous and isoenergetic diets were fed to white shrimp with an initial body weight of 2.96 g for 42 days. The positive group showed the highest weight gain (WG) and the lowest feed conversion ratio (FCR), and the negative group had the lowest WG and the highest FCR among all groups. The supplementation of coated amino acids or protease tended to improve WR, and decrease FCR(P>0.05)when compared to the negative control. The combined supplementation of coated amino acids and protease improved WR by 11.5%, decreased FCR by 0.18(P<0.05), and significantly promoted protein retention and digestibility of dry matter and crude protein (P<0.05). There were no significant differences in moisture, crude protein, crude lipid and ash contents of whole body among groups (P>0.05), and all groups showed no significant differences in lipid retention and activities of lipase and amylase in hepatopancreas (P>0.05). The above results showed that the supplementation of 500 mg/kg coated lysine, 900 mg/kg coated methionine or 175 mg/kg protease in a low fish meal diet (15% fish meal) did not significantly influence the growth, but the combined supplementation of coated amino acids and protease significantly improved the growth and nutrients utilization of white shrimp.