Effects of Bacillus subtilis DSM 32315 (Gutcare®) on the growth performance, antioxidant status, immune ability and intestinal function for juvenile Litopenaeus vannamei fed with high/low-fishmeal diets

Abstract

This study was conducted to investigate the effects of dietary Bacillus subtilis DSM 32315 (Gutcare®) supplementation on the growth performance, antioxidant status, immune ability and intestinal function in juvenile Litopenaeus vannamei fed with high/low-fishmeal diets. A 4 × 2 two-factor design was formulated with graded dietary Gutcare® and fishmeal levels. Specifically, four Gutcare® supplemental levels (0, 0.05%, 0.15% and 0.3%) were added under two fishmeal diets (20% and 5% fishmeal levels). Each diet was randomly assigned to five replicate groups of 30 juvenile Pacific white shrimp that were stocked in fiberglass tanks. The results indicated no significant inhabitation on the growth performance, hepatopancreas antioxidant capacity, immune response and intestinal function at 5% fishmeal compared with 20% fishmeal. Shrimp fed with Gutcare® supplementation regardless of high/low-fishmeal diets exhibited higher growth performance, antioxidant- and immune-related enzyme activities (P < 0.05) compared with that 0% Gutcare® supplementation. However, none of the treatments found significant differences in feed efficiency and survival. The mRNA expression levels of Cu/Zn superoxide dismutase, heat shock protein 70, glutathione peroxidase, prophenoloxidase and lysozyme were significantly up-regulated (P < 0.05) at shrimp fed with Gutcare®. Moreover, the results of mid-intestine morphology showed a significant increase with the addition of Gutcare®, and the highest height and thickness of intestinal epithelium occurred at shrimp fed 0.15% Gutcare®. Bacterial community composition showed that shrimp fed with the graded Gutcare® significantly increased the abundance of Firmicute and reduced the relative abundance of Vibrio (P < 0.05). In conclusion, 5% fishmeal supplementation with well-balanced amino acid composition had no adverse effect on the growth performance of L. vannamei when compared with the 20% fishmeal. Dietary Gutcare® significantly enhanced immunity and antioxidant capacity, and improved intestinal function of L. vannamei. The positive effect of Gutcare® at 5% fishmeal diet provided a possibility for reducing fish meal in the commercial diets of Pacific white shrimp.