Assessment of the Effects of Edible Microalgae in a Canine Gut Model

SIMPLE SUMMARY: The gut microbiota plays a crucial role in maintaining host health and is considered a potential target of novel therapeutics. Microalgae represent an interesting source of bioactive compounds for nutritional supplementation in humans and animals. However, there is a lack of information on the effects of microalgae on canine gut microbiota. The present study investigated for the first time the effects of four microalgae (Arthrospira platensis, Haematococcus pluvialis, Phaeodactylum tricornutum, Chlorella vulgaris) on some fecal bacterial populations and metabolites, such as SCFA, BCFA, ammonia and biogenic amines, in an in vitro canine gut model. Following the in vitro fermentation, chemical and microbiological analysis displayed significant differences between the control and microalgae groups, particularly the Phaeodactylum tricornutum group. Nonetheless, further investigations are needed to better understand the potential inclusion of these notable natural resources in pet nutrition. ABSTRACT: Microalgae are a source of bioactive compounds having recently been studied for their possible application as health-promoting ingredients. The aim of the study was to evaluate in an in vitro canine gut model the effects of four microalgae, Arthrospira platensis (AP), Haematococcus pluvialis (HP), Phaeodactylum tricornutum (PT) and Chlorella vulgaris (CV), on some fecal microbial populations and metabolites. The four microalgae were subjected to an in vitro digestion procedure, and subsequently, the digested biomass underwent colonic in vitro fermentation. After 6 h of incubation, PT increased propionate (+36%) and butyrate (+24%), and decreased total BCFA (−47%), isobutyrate (−52%) and isovalerate (−43%) and C. hiranonis (−0.46 log10 copies/75 ng DNA). After 24 h, PT increased propionate (+21%) and isovalerate (+10%), and decreased the abundance of Turicibacter spp. (7.18 vs. 6.69 and 6.56 log10 copies/75 ng DNA for CTRL vs. PT, respectively); moreover, after 24 h, CV decreased C. coccoides (−1.12 log10 copies/75 ng DNA) and Enterococcus spp. (−0.37 log10 copies/75 ng DNA). In conclusion, the microbial saccharolytic activities and the shift in fecal bacterial composition were less pronounced than expected, based on current literature. This study should be considered as a preliminary assessment, and future investigations are required to better understand the role of microalgae in canine nutrition.