Dietary protein and lipid optimum requirements for on-growing golden Pompano (Trachinotus ovatus)

Abstract:

Six isolipidic practical diets were formulated to contain different levels of fish meal (six graded protein levels were named P1-P6 respectively). Fish was fed by hand twice daily until apparent satiation. The growth performance of fish including weight gain rate as well as protein efficiency rate significantly increased (P<0.05) with increasing dietary protein levels (P1-P6) and then kept steady (P>0.05). Growth performance of fish fed P4, P5 and P6 was significantly higher than that of fish fed P1, P2 and P3 (P<0.05). While feed conversion ratio and feed intake decreased significantly (P<0.05) with increasing levels of dietary protein up to 49.75% and remained nearly the same thereafter. Feed conversion ratio and feed intake in P4 and P5 were significantly lower than those of fish fed P1, P2 and P3 (P<0.05). Regression analysis showed that the recommended optimum dietary protein level for on-growing golden pompano was 49.75% (mass fraction). On the basis of dietary protein requirement, another 12-week feeding trial was conducted to evaluate dietary lipid requirement for on-growing golden pompano. Six isocaloric practical diets were formulated to contain different levels of soybean oil (six graded lipid levels were named L1-L6 respectively). With the increase of dietary lipid levels (L1-L6), growth performance of fish including weight gain rate and protein efficiency rate first significantly increased and then kept steady (P>0.05). Growth performance of fish fed L3, L4, L5 and L6 was significantly higher than that of fish fed L1 and L2 (P<0.05). Feed conversion ratio and feed intake decreased with increasing levels of dietary lipid up to 12.20% and remained nearly the same thereafter. Feed conversion ratio and feed intake in L3, L4, L5 and L6 were significantly lower than those of fish fed L1 and L2 (P<0.05). Regression analysis showed that the recommended optimum dietary lipid level for golden pompano (121-580 g) was 12.20%-12.27% (mass fraction).