Effects Of Fish Meal Substitution Diets Supplemented With Mineral Premix On The Growth Of Litopenaeus Vannamei Reared In Low Salinity Water

A feeding trial was conducted to determine the effects of mineral composition of low-fishmeal diets on growth performance and tissues mineralization of juvenile shrimp Litopenaeus vannamei reared in low-salinity water. Nine isoproteic and isolipdic practical diets were formulated. The control diets, FM and FMR, contained 30% fish meal; Sixty percent fish meal of FM was replaced by soybean meal to formulate soybean-meal diets(SB, SBF, SBR and SBRR), and one hundred percent fish meal of FM was replaced by poultry by-product meal to formulate poultry-byproduct-meal diets(PBF, PBR and PBRR). Meanwhile, FM and SB weren’t supplemented with minerals; SBF and PBF with mineral supplementations had the same mineral compositions to FM; FMR, SBR and PBR were supplemented with minerals according to mineral requirements of shrimp; SBRR and PBRR had same macroelement contents to SBR and PBR, respectively, but double microelement levels. The juvenile shrimps with initial weight 0.18±0.01 g were fed in 27 tanks(available volume of 100L) for 8 weeks at 2‰ salinity. The results showed that:1. The effects of dietry mineral levels on growth performance, non-specific immune factors and osmoregulation of Litopenaeus vannameiThe growth performance, muscle composition, hepatic digestive enzyme activity, phenoloxidase(PO) and superoxide dismutase(SOD) activity in serum, catalase(CAT) and glutathione peroxidase(GSH-PX) in hepatopancreas,serum osmotic pressure and gills ATPase activity of FMR and FM were not significantly different(P>0.05). SB had significantly lower weight gain(WG) and protein efficiency rate than other groups(P<0.05). There was no significant difference in WG among PBF, FMR, FM and PBRR(P>0.05), but the WG of PBF was significantly lower than PBR, SBF, SBR and SBRR(P<0.05). The SB, SBF, SBR and SBRR had significantly higher feed efficiency than other groups(P<0.05). And the crude protein and lipid content in muscles of SBF, SBR and SBRR were higher than other groups. Compared with other groups, the SB had significantly lower hepatic protease activity(P<0.05). The lipase and amylase activity of hepatopancreas have no significant differences among all groups(P>0.05). The serum PO activity of SB was significantly lower than SBF, SBR and SBRR(P<0.05). FM and SB had significantly higher hepatic alkaline phosphatase activity than other groups(P<0.05). The T-ATPase, Na/K-ATPase, Ca/Mg-ATPase activity in gills of SB were significantly higher than other groups(P<0.05), conversely, its serum osmotic pressure was lowest. The protein apparent digestibility of SB was significantly higher than other groups, while SB had significantly lower dry-matter and ash apparent digestibility(P<0.05). The apparent digestibility of dry-matter and ash in FMR, PBF and SBF were significantly higher than other groups(P<0.05).2. The effects of dietry mineral levels on tissues mineralization and mineral element apparent digestibility of Litopenaeus vannameiCompared with other groups, SB had significantly lower Ca content in whole body, muscle and exoskeleton(P<0.05), and the Ca, P, Na, K and Mg content in whole body of other groups had no significant differences(P>0.05). The whole body Fe, Cu and Mn content of SBF were significantly lower than other groups(P<0.05). FMR, PBR and PBRR had significantly higher Mn content in whole body than other groups(P<0.05). What’s more, PBRR and SBRR had significantly higher Cu content in whole body, muscle, hepatopancreas and serum(P<0.05). Apart from SB or SBF, the Ca, P, Na, K, Mg, Fe and Zn content in muscle and exoskeleton and the Ca and Zn content in serum had no significant differences among other groups(P>0.05). PBR and PBRR had significantly higher Mg content in serum than FM and PBF(P<0.05). The serum Mn content of SBR and SBRR were significantly higher than other groups(P<0.05). FMR, FM, PBF and SBF had significantly higher Ca apparent digestibility than those in other groups(P<0.05). The Ca apparent digestibility of SBR and SBRR were significantly higher than SB, PBR and PBRR(P<0.05). And the P apparent digestibility of SBF, SBR and SBRR were significantly higher than other groups(P<0.05). The apparent digestibility of Mg, Cu and Mn in FMR, PBR PBRR, SBR and SBRR were significantly enhanced by supplementation of Mg, Cu and Mn elements(P<0.05).In conclusion, our present results indicated that it was necessary for low-fishmeal diets to be supplemented with mineral elements to compensate for negative effects of their unbalanced mineral composition on growth performance or tissues mineralization of juvenile Litopenaeus vannamei reared in low-salinity water. With mineral element supplementations, muscle protein deposition, osmoregulation and PO activity of Litopenaeus vannamei fed high soybean protein diets could be markedly improved. Additionally, mineral element apparent digestibility of entire poultry-byproduct-meal diets or high soybean protein diets were enhanced by mineral element supplementations, which made their shrimps having similar tissue mineralizations to Litopenaeus vannamei fed fish-meal diets.