Comparison of Germination and Intestinal Morphological Modification of Candidate Probiotics in Aquaculture Species

The application of microbial products as digestive health and immunological stimulants in animal feeds is a rapidly growing field of commercial interest and study. Aquaculture, the fastest growing sector in animal production, is experiencing broad adoption of probiotics with varying degrees of reproduced investigation. Exploring and verifying the specific dynamics of host-probiont interactions is becoming increasingly important. Evaluation of probiotic effects and subsequent marketing in aquaculture is often delineated by microbial species. This study focused on differentiating basic growth and effects of four Bacillus spp. as direct-fed microbes, delivered as spores on extruded feed to a model aquaculture species: rainbow trout. During this 6-week study, growth metrics were tracked to compare health and performance between treatments. Germination in three distinct intestinal regions was quantified with a differential qPCR method. Modification of intestinal morphology was indicated by microvilli length. Different germination rates, spatial preference in the trout gastrointestinal tract (GIT) and morphological effects were found between candidate probionts. We outline the importance of emphasizing strain differentiation in probiotic screening and identify intestinal morphological effects between candidate probiotic strains for aquacultured finfish.