Effects of five compound attractants in high plant-based diets on feed intake and growth performance of juvenile turbot (Scophthalmus maximus L.)

An experiment was conducted to evaluate the effects of five attractants on feed intake, growth performance and appetite-regulating genes expression for juvenile turbot (Scophthalmus maximus L.). Fish were fed with seven diets: fish-meal-based diet (FM), fermented soybean meal replacing 45% fish meal (FSBM) and other diets with 1% compound attractant A (CA-A) consisting of amino acids, compound attractant B (CA-B) consisting of quaternary ammonium bases, compound attractant C (CA-C) consisting of nucleotides, compound attractant G (CA-G) consisting of the combination of CA-A, CA-B and CA-C and blue mussel protein hydrolysate (BMH) on the basis of FSBM diet respectively. Daily feed intake in CA-A group was significantly higher, but that in CA-B group was significantly lower than FSBM group. Similarly, specific growth rate was significantly enhanced in CA-A and CA-G groups and were significantly decreased in CA-B group. Protein efficiency ratio and protein retention in CA-B group were significantly lower than FSBM group. Furthermore, BMH supplement increased the mRNA expression of Ghrelin in the intestine of fish. These results showed that CA-A and CA-G supplement could enhance growth in plant-based diets, but CA-B supplement had the opposite effect, which might be associated with lower feed intake and lower feed utilization.