Functional and mechanistic studies of a phytogenic formulation, Shrimp Best, in growth performance and Vibriosis in whiteleg shrimp

Abstract

Climate change and disease threaten shrimp farming. Here, we conducted a functional and mechanistic study of the administration of a phytogenic formulation, Shrimp Best (SB), to whiteleg shrimp, and assessed their health and growth performance. First, SB was found to increase shrimp body weight by 2.75 to 20.93% and decreased feed conversion ratio by 8–21% compared to control shrimp at 28 days post feeding in aquaria. The data were verified by field trials. Next, we tested the effect of SB on vibriosis in shrimp. SB protected against Vibrio parahaemolyticus as evidenced by survival rate, bacterial load, and hepatopancreatic pathology in shrimp. Finally, we explored the likely mechanism of SB for growth performance and anti-Vibrio protection in shrimp. We initially examined gut microbiota in control shrimp and shrimp fed with SB. The 16S rDNA sequencing data showed that SB increased 6 probiotic genera and decreased 6 genera of pathogenic bacteria in shrimp. Furthermore, Lactobacillus johnsonii, L. reuteri and V. parahaemolyticus were identified from shrimp guts using a serial dilution culture and mass spectrometry. Consistently, polymerase chain reaction data confirmed that SB increased the proportion of L. johnsonii and decreased that of V. parahaemolyticus in shrimp guts. To dissect the relationship among SB, Lactobacillusand Vibrio, we investigated the in vitro regulation of probiotics and pathogenic bacteria by SB. SB at ≥ 0.25 μg/mL promoted growth of L. johnsonii whilst SB at ≥ 200 μg/mL was able to inhibit V. parahaemolyticus growth. Additionally, antagonistic studies revealed that L. johnsonii and its culture supernatant could inhibit V. parahaemolyticus but not vice versa. Furthermore, five anti-Vibrio metabolites, identified from the supernatant of L. johnsonii using liquid chromatography coupled with mass spectrometry were up-regulated by SB. This anti-Vibriomechanism involved destruction of the bacterial membrane. In parallel, we also identified linoleic acid, linolenic acid, and stearic acid as active compounds from SB. Overall, this work demonstrated that SB improved growth performance and vibriosis in shrimp by regulation of gut microbiota, suggesting that SB is a promising phytogenic for shrimp growth and disease control.