The supplementation of aquatic animal by-products hydrolysates can effectively improve the nutritional value of low fish meal feed for largemouth bass, Micropterus salmoides

Abstract

Abstract The study was conducted to investigate the effects of aquatic animal by-products hydrolysates (AH) inclusion on the nutritive value of low-fishmeal diet for largemouth bass. The diet with 45% and 25% fishmeal was regarded as positive control (PC) and negative control (NC), respectively, and another three diets were prepared by the supplementation of shrimp hydrolysate powder (SHP) or by top-coating 1.5% of tuna visceral hydrolysate (TH) and shrimp by-product hydrolysate (SH) in the low fishmeal diet. Triplicate group of fish with initial body weight of 10.12 ± 0.02 g were fed one of the experimental diet twice daily for 62 days. The results of feeding trial revealed that the inclusion of AH, especially SHP, significantly alleviate the negative effects on growth performance caused by the low fishmeal diet. The beneficial role of AH supplementation partly related to the improved feed utilization, including FI, FER and PER. Although no significant difference was observed in the crude protein content of whole fish body, the inclusion of AH significantly decreased the low fishmeal diet caused the elevated moisture content. Meanwhile, the low fishmeal diet significantly decreased the crude lipid content of whole fish body, which was reversed by AH inclusion. The activity of serum lysozyme was significantly decreased by low fishmeal diet, but elevated with the inclusion of AH inclusion. Meanwhile, the inclusion of AH alleviated the low fishmeal diet induced the increased activity of AST. Additionally, the low fishmeal diet resulted in the decrease of total antioxidant capacity (T-AOC) and SOD activity, while the AH supplementation improved the negative effects on antioxidant capacity. No significant difference was observed in the expression of IGF-1 among treatments. The expression of TOR was significantly reduced by low fishmeal diet, and the AH inclusion elevated its expression. In conclusion, the inclusion of AH benefits for improving the nutritive value of low fishmeal diet for largemouth bass.