Evaluation of methanotroph (Methylococcus capsulatus, Bath) bacteria meal as an alternative protein source for growth performance, digestive enzymes, and health status of Pacific white shrimp (Litopenaeus vannamei).

The increasing cost of fishmeal (FM) with limited supply and the continuous development of aquaculture necessitate more economical FM substitutes. This study aimed to appraise the effects of dietary methanotroph (Methylococcus capsulatus, Bath) bacteria meal, a kind of methane-utilizing bacteria protein (MBP), replacing fishmeal on the growth and feed utilization, serum biochemical parameters, antioxidant status, and digestive enzyme activities of Pacific white shrimp (Litopenaeus vannamei). Seven isonitrogenous and isoenergetic diets were designed with 0%, 6.89%, 13.92%, 21.09%, 28.40%, 35.85%, and 43.46% MBP replacing FM, and fed to Pacific white shrimp (mean initial weight 0.27 ± 0.02 g) for 8 weeks. The shrimp fed with 28.40%, 35.85%, and 43.46% MBP diets showed significantly higher weight gain and specific growth rate compared to the control group (P < 0.05), while the other MBP diets had no significant effect on the growth performance (P > 0.05). No statistical differences were found in the activities of digestive enzymes in the stomach, hepatopancreas, and midgut among shrimp fed the dietary treatments (P > 0.05). Furthermore, antioxidant parameters in serum and hepatopancreas showed no significant differences among all the groups (P > 0.05). In conclusion, it was revealed that MBP replacing from 28.40 to 43.46% FM in the diet with appropriate supplementation of essential amino acids significantly improved the growth of Pacific white shrimp without adverse effects on feed utilization, digestive enzyme activities, physiological condition, and antioxidant status. This study provides a reference for replacing FM with MBP in the diet of Pacific white shrimp. [ABSTRACT FROM AUTHOR]