Use of a mixture of barley-based fermented grains and wheat gluten as an alternative protein source in practical diets for Litopenaeus vannamei (Boone)

A combination of barley-based fermented grains (BFG) and wheat gluten (WG) meal (1:1 on a crude protein basis) was evaluated as an alternative protein-rich ingredient (BFG–WG) in diets for juvenile Litopenaeus vannamei. Four isocaloric diets were formulated to contain 44% protein in which protein from BFG–WG replaced 0% (A), 33% (B), 66% (C) and 100% (D) of the protein from marine animal protein (MAP: 69% shrimp head meal, 21% fish meal and 10% squid meal) in the diets. These diets were delivered twice a day for 6 weeks to shrimp (initial weight±standard error, 2.14±0.02 g). Shrimp fed diets A (control) and B showed similar weight gain at the end of the experiment. There were no significant differences among the survival rates of different dietary treatments (>96%). The amount of uneaten food was positively and significantly (r2=0.57, P<0.001) related to the level of inclusion of BFG–WG in the diets, suggesting that diet palatability was a major factor influencing shrimp growth. Diet D had the highest apparent digestibility for protein and dry matter. The inclusion of BFG–WG had a positive effect (r2=0.75, P<0.05) on carbohydrate digestibility. A significant stimulation of amylase activity and soluble protein and glycogen concentrations in the hepatopancreas also was related to the amount of BFG–WG in the diet. Feed conversion ratio and protein efficiency ratio were not significantly different among diets containing substitution levels of 0%, 33% and 66% of MAP, which could suggest that if the balance of amino acids and the palatability in the diet can be improved, replacement level of the MAP may be increased to 66% without reducing growth.