Effects of fish meal replacement by Clostridium autoethanogenum protein on growth performance, serum biochemistry, antioxidant capacity, immune responses and muscle quality in black carp (Mylopharyngodon piceus)

The study investigated the growth performance, serum biochemistry, antioxidant and immune responses, and muscle quality of black carp (Mylopharyngodon piceus) fed dietary fish meal replaced by Clostridium autoethanogenum protein (CAP) (0 %, 20 %, 40 %, 60 %, 80 %, and 100 %), which were named CAP0 (control), CAP20, CAP40, CAP60, CAP80, and CAP100, respectively. A total of 450 juvenile black carp (initial body weight: 5.34 ± 0.02 g) were randomly allocated into six experimental groups. Results showed there were no differences on growth in black carp fed six CAP-level diets. Contents of insulin-like growth factor Ⅰ (IGF-Ⅰ) and 5-hydroxytryptamine (5-HT) were increased in CAP60 group. CAP40 showed reduced activities of serum alanine aminotransferase (ALT), and aspartate aminotransferase (AST), while increase lysozyme (LZM), and immunoglobulin M (IgM) levels compared to CAP100 group. Although kelch-like ECH associated protein 1α (keap1α) were decreased in CAP60 group, glutathione peroxidase 1 (gpx1) mRNA levels were heightened in the hepatopancreas of CAP40 and CAP60 groups. There were no differences on activities of total superoxide dismutase (T-SOD) and catalase (CAT) among CAP0, CAP20 and CAP40 groups. CAP40 exhibited increased intestinal villi height (VH) values together with claudin-5 (cldn-5) levels compared to CAP0 group. Meanwhile, CAP40 increased values of hardness and springiness, and expression levels of collagen 1α1 (col1α1), prolyl hydroxylase (phd) and lysyl oxidase (lox) in muscle compared to CAP100 group. In conclusion, 40 % fish meal replacement with CAP could improve serum biochemical indices, antioxidant capability, immune responses, muscle texture and quality in black carp.