Effects of long-term dietary supplementation of β-1,3-glucan on growth performance, body composition and biochemical indices of Litopenaeus vannamei.

A 12-week feeding trial was conducted to study the effects of β-1,3-glucan on growth performance,body composition and biochemical indices of Litopenaeus vannamei.Six hundred and forty shrimp of Litopenaeus vannamei with the initial body weight of (0.43±0.01) g were randomly divided into 4 groups with 4 replicates each and 40 shrimp in each replicate.Group Ⅰ,as the control group,was fed the basal diet,while groups Ⅱ,Ⅲ and Ⅳ,as trial groups,were fed the basal diets supplemented with 250,500 and 1 000 mg/kg β-1,3-glucan,respectively.The results showed as follows:the final body weight (FBW),weight gain rate (WGR) and specific growth ratio (SGR) of Litopenaeus vannamei were increased firstly and then decreased with the β-1,3-glucan level increasing.The highest values of FBW,WGR and SGR were found in group Ⅱ.Compared with the control group,protease and lipase activities in hepatopancreas were significantly increased in group Ⅲ (P0.05),while amylase activity in hepatopancreas was significantly increased in groups Ⅱ and Ⅲ (P0.05).Total protein (TP),cholesterol (CHO) and triglyceride (TG) contents in serum,and glycogen content in hepatopancreas were higher in group Ⅱ than those in the control group (P0.05).No significant differences were observed in glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) activities in hepatopancreas,glucose (GLU) content in serum,and glycogen,CHO and TG contents in muscle among all groups (P0.05).Compared with the control group,serum catalase (CAT) and lysozyme (LSZ) activities in group Ⅳ were significantly increased (P0.05),and serum alkaline phosphatase (ALP) activity in group Ⅲ was significantly increased (P0.05).No significant differences were observed in superoxide dismutase (SOD) and acid phosphatase (ACP) activities in serum among all groups (P0.05).β-1,3-glucan supplementation could not affect the moisture,crude protein,ether extract and ash contents in the whole body of Litopenaeus vannamei (P0.05).In conclusion,1) long-term supplementation of 250 mg/kg β-1,3-glucan in diets can improve the growth performance,and promote the metabolism of nutrients in Litopenaeus vannamei;2) long-term supplementation of 500 or 1 000 mg/kg β-1,3-glucan in diets can improve the non-specific immune ability in Litopenaeus vannamei.