Replacement of fish meal with Methanotroph (Methylococcus capsulatus, Bath) bacteria meal in the diets of Pacific white shrimp (Litopenaeus vannamei)

Methanotroph (Methylococcus capsulatus, Bath) bacteria meal is a kind of bacterial protein meal (BPM) with an excellent nutrition profile. This study evaluated the effects of replacing fish meal (FM) with BPM on growth, antioxidant capacity, intestinal morphology, and gut microbiota of Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated to contain 25% FM, then 15, 30 and 45% of FM was replaced with BPM, which were identified FM, BPM15, BPM30, and BPM45 diets, respectively. Triplicate groups (40 shrimp per replicate) of shrimp (0.88 +/- 0.01 g) were fed the test diets to apparent satiation four times daily for 7 weeks. There were no significant differences in growth performance among four groups. Malondialdehyde content and anti-oxidative enzymes activity in hepatopancreas were significantly increased with increasing BPM levels. For intestinal histology, the circular muscle layer thickness was significantly increased in BPM45. The mucosal folds height of shrimp fed BPM45 was significantly higher than those fed BPM15. The width of mucosal folds in BPM15 and BPM30 was significantly reduced comparing with FM. Transmission electron microscopy results showed that intestinal microvilli was impaired and endoplasmic reticulum stress was present in shrimp fed BPM45 diet. However, dietary BPM improved the diversity of intestinal microbiota, and more beneficial microbiota such as Pseudoalteromonas, Ruegeria, and Lactobacillus, as well as less harmful microbiota such as Vibrio were found in the gut of BPM45. A 12-day challenge study with Vibrio parahaemolyticus showed that shrimp fed diet BPM15 had a significantly lower mortality throughout the challenge trial. To conclude, BPM replacement of fish meal did not affect growth performance and feed utilization of shrimp. The high dietary inclusion of BPM increased the oxidation level in the hepatopancreas of shrimp and BPM was able to increase the height of the mucosal folds, improve the gut microbiota structure and increase the disease resistance of shrimp.

Automated summary

The study showed that replacing fish meal with methanotroph bacteria meal had no significant impact on the growth performance of Pacific white shrimp, but it did increase the oxidation level in the hepatopancreas and improve the gut microbiota structure, enhancing the disease resistance of shrimp.