A composition comprising Bidens pilosa or an active compound isolated from the Bidens pilosa for use in treating, inhibiting and/or decreasing the presence of pathogenic gut microbiota in an animal in need thereof is disclosed. The pathogenic gut microbiota are at least one selected from the group consisting of Brachyspira, porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis coronavirus (TGEV) and Rotavirus (RV). The composition is also for use in treating, inhibiting and/or decreasing occurrence of swine diarrhea, swine dysentery, swine viral infection and increasing the percentage of swine carcass and bone weight. In one embodiment, the composition is for use in treating, inhibiting and/or decreasing occurrence of swine dysentery associated with Brachyspira.