Optimum dietary levels of lysine and methionine reduces the crude protein requirement and improves growth in Snubnose pompano (Trachinotus blochii)

This study was aimed to test the effects of lysine (Lys) and methionine (Met) intake at different dietary protein levels (36, 38, and 40 g/100 g crude protein) on growth and metabolism in the juveniles of silver pompano (Trachinotus blochii). The experiment comprised six diets with different protein levels (CP 36, 38, and 40 g/100 g) without (D1, D2, D3) and with (D4, D5, D6) the supplementation of crystalline Lys (2.40 g/100 g) and Met (1.19 g/100 g). The diets were fed to the juveniles of silver pompano (average initial weight of 4.69 g) stocked in a recirculatory aquaculture system. After the feeding trial, the growth and nutrient utilization parameters in terms of weight gain percentage (WG %), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) increased significantly (P < 0.05) with an increase in the dietary crude protein levels and supplementation of Lys and Met. There were no significant differences in the growth and feed utilization among the groups D3, D4, D5 and D6, while the lowest values were observed in D1 (weight gain = 288.31%, SGR=1.50, FE=0.40). However, no significant differences were found in the levels of serum triglycerides, hepatosomatic index (HSI), viscerosomatic index (VSI), serum cholesterol, serum albumin- to- globulin ratio (A: G) and whole-body lipid and moisture contents. In conclusion, the supplementation of optimum levels of Lys (2.40 g/100 g) and Met (1.19 g/100 g) in feed, with dietary protein level of 38 g/100 g, is sufficient for silver pompano and was found to result in better growth