Effects of Dietary Protein and Vitamin B_6 Levels on Growth and Aminotransferase Activities of Pacific White Shrimp (Litopenaeus vannamei) at Low Salinity

A feeding trial was conducted to investigate the effects of dietary protein and vitamin B6 levels on growth and amino transferase activities of juvenile Pacific white shrimp (Litopenaeus vannamei,L.vannamei). Purified basal diets were formulated using vitamin-free casein as the protein source. Two levels (0 and 200 mg/kg diet) of vitamin B6 were added to the 2 basal diets which contained 25.5% and 40.8% dietary protein,respectively. Four hundred and eighty shrimp with an average body weight of (0.014 4±0.004 7) g were randomly allotted to 4 groups with 3 replicates of 40 shrimp. The trial lasted for 30 d and the salinity was 3‰. Results showed that supplementation of vitamin B6 200 mg/kg in diet could significantly increase the weight gain ratio (WGR),survival rate (SR),condition factor (CF) and activities of glutamic oxaloacetic transferase (GOT) and glutamic pyruvic transferase (GPT) of L.vannamei (P0.05); the WGR,CF and activities of GOT and GPT of L.vannamei fed diets containing 25.5% and 40.8% protein had no significant differences (P0.05),but SR in 40.8% protein group was significantly higher than that in 25.5% protein group. The Two-way ANOVA results showed that there was no significant interaction between dietary protein and vitamin B6 in all parameters of L.vannamei at low salinity (P0.05). All results in this study indicated that dietary vitamin B6 and protein had different nutritional effects on L.vannamei,and when preparing diets for L.vannamei cultured at low salinity,dietary vitamin B6 and protein must meet the requirement of L.vannamei at the same time. It was infeasible to try to meet or increase one of those 2 nutrients to get the maximum growth and survival rate of L.vannamei with the aim to spare the other nutrient.