Dietary Bromelain From Pineapple Extracts Enhanced Growth Performance and Modulated Stomach Microbiota Which Provided Longer-Term Protection to Penaeus vannamei Against Acute Hepatopancreatic Necrosis Disease (AHPND) Caused by Vibrio parahaemolyticus

Abstract

The emergence of acute hepatopancreatic necrosis disease (AHPND) caused by pathogenic strains of Vibrio parahaemolyticus (VP_AHPND) had economically impacted shrimp farmers. There is great interest in using phytogenics as antibiotic alternatives in mitigating bacterial diseases. A 28-day feeding trial using quadruplicate groups of Penaeus vannamei was conducted to evaluate the efficacy of bromelain (BM), a pineapple extract, on growth, gut microbiota, and resistance to AHPND. Dietary 1% or 2% BM enhanced growth of shrimp, which was significantly (P  < 0.05) higher at 2% BM compared to control (0% BM). In the first AHPND challenge, shrimp survival (mean ± SE) fed 1% or 2% BM were 84.8% ± 3.8% and 78.3% ± 2.5%, respectively, and significantly higher compared to the positive control group (69.6% ± 1.8%). Surviving shrimp were then regrouped into triplicates and fed the control diet for 14 days. This wash-out period was used to determine if prior dietary BM had a longer-term effect on shrimp health. In the second AHPND challenge, shrimp survival previously fed 1% or 2% BM was 71.1% ± 9.7% and 73.3% ± 3.8%, respectively, and significantly higher compared to the control group (51.1% ± 2.2%). Hepatopancreas showed less damage and harbored significantly lower Vibrio counts in shrimp fed BM-added diets. Dietary BM modulated the stomach bacterial community and imparted the highest alpha diversity. At the phylum level, Proteobacteria, Actinobacteria, and Bacteroidetes were the main groups across treatments but with varying relative abundance. Luteolibacter, Paracoccus, Planctomyces, and Demequina were identified as the main contributors for the diversity differences observed among treatment groups. The relative abundance of Luteolibacter was significantly enriched and Vibrio bacteria significantly lowered in the stomach of the BM-added groups. It was concluded that dietary BM induced modulation of the stomach microbiota of shrimp, which potentially enhanced its resistance to AHPND-causing VP.