Bovine bone meal combined with dephenolized cottonseed protein is an effective fishmeal substitution in Trachinotus ovatus feed: A comprehensive evaluation of growth, muscle quality, and intestinal digestion physiology

To investigate the feasibility of substituting fishmeal (FM) with a combination of bovine bone meal (BBM) and dephenolized cottonseed protein (DCSP), a mixture (consisting of 60 % BBM and 40 % DCSP) was used to replace varying FM levels in Golden pompano (Trachinotus ovatus) feed. Five isoproteic (47 %) and isolipidic (12 %) experimental diets were formulated, with FM levels set at 30 %, 24 %, 18 %, 12 %, and 6 % (namely Control, FM24, FM18, FM12, and FM6). To compensate for the reduced FM content, BBM and DCSP were used as substitutes, and DL-methionine and L-lysine were added to maintain the dietary amino acid balance. Following a 63-day trial, results showed that the growth of FM24, FM18 and FM12 groups did not exhibit significant differences compared to the Control group, while those of FM6 group considerably decreased. The biochemical composition of whole fish did not display significant differences among the five groups, while the muscle protein contents of the FM12 group were higher than the Control group. Most of the muscle texture properties were positively modified in the FM 12 and FM 6 groups. With the substitution ratio increase, the contents of serum total protein, albumin, total amino acids, and cholecystokinin were elevated, while serum peptide YY contents decreased. In addition, intestinal trypsin, NaK-ATPase, and alkaline phosphatase activities in FM18, FM12, and FM6 groups decreased, and lipase activities exhibited the opposite trend. The transcription levels of genes related to amino acid-sensing receptors (asct2 and snat2) were down-regulated with increasing dietary FM substitutions, while the expression levels of appetite regulation factors (pept1, cck, and ghrl) were up-regulated. In conclusion, the FM content in the diet of T. ovatus can be reduced to 12 % through the utilization of a combination of BBM and DCSP, with no adverse effects observed on growth performance, biochemical composition, or muscle texture.