Enhanced intestinal health, immune responses and ammonia resistance in Pacific white shrimp (Litopenaeus vannamei) fed dietary hydrolyzed yeast (Rhodotorula mucilaginosa) and Bacillus licheniformis

Abstract

To explore the impacts of dietary hydrolyzed yeast (Rhodotorula mucilaginosa) and Bacillus licheniformis (B. licheniformis) on the growth, intestinal histology, innate immune response and ammonia resistance of Litopenaeus vannamei, four experimental diets (basal diet (Control); 0.5 % hydrolyzed yeast (HY); 0.1 % B. lincheniformis (BL) and 0.5 % hydrolyzed yeast + 0.1 % B. licheniformis (SYN)) were fed shrimps for 8 weeks. Results showed no significant differences on growth and body composition among all treatments, while a significantly higher feed efficiency (FE) in shrimp fed BL diet and a significantly higher protein efficiency ratio (PER) in shrimp fed BL and SYN diets were found compared to those in shrimp fed the Control diet (P < 0.05). At week 4, significantly higher intestinal villus height in shrimp fed supplemented diets were observed (P < 0.05). At week 8, significantly higher villus number in shrimp fed BL and SYN diets, and significantly higher villus height in shrimp fed supplemented diets were observed compared to those in shrimp fed the Control diet (P < 0.05). Compared to Control diet, the GPX, SOD and ACP activities were significantly increased, and the MDA content was decreased in hepatopancreas of shrimp fed supplemented diets (P < 0.05). The expression levels of CAT, GPX, SOD, Pen-3a and PPO were upregulated by supplemented diets at week 1, 2, 4 and 8. In addition, the expression levels of these genes, especially Pen-3a and SOD, were appeared in a trend of first increased and then decreased during the feeding. After ammonia challenge at week 8, shrimps fed HY and SYN diets showed significantly higher survival rate than that in shrimp with the Control diet (P < 0.05). Furthermore, the expression of Pen-3a, PPO and SOD in supplemented treatments were significantly upregulated after ammonia challenge. Results demonstrated that either dietary hydrolyzed yeast, B. licheniformis or their combination showed no significant effects on growth performance and body composition, but affected intestinal health, immune responses and ammonia resistance of Litopenaeus vannamei.

Keywords

• Hydrolyzed yeast
• Bacillus lincheniformis
• Intestinal histology
• Ammonia stress
• Litopenaeus vannamei