PSI-20 Herbal extract supplementation as a functional ingredient in modulating canine gut microbiome and biomarkers of gut health.

Abstract Herbal extracts have gained popularity for their functional properties due to their phenolic compounds and phytochemicals. Humans have a long history of utilizing these herbal extracts and their phytochemicals for their medicinal properties, including antioxidant, antimicrobial, and digestive health promoting effects. The objective of this study was to determine the effects of different inclusion rates of an herbal extract mixture (cinnamon, tea, and pomegranate hydrogenated vegetable oil) on apparent total tract digestibility (ATTD) of macronutrients and fecal metabolites, microbiota, and biomarkers in adult canines. This study used a complete randomized design with 32 canines fed a complete and balanced chicken and rice diet formulated to meet the nutritional requirements of adult canines (AAFCO, 2024) containing different inclusion rates of the herbal extract mixture: Control (0 ppm), Diet 1 (100 ppm), Diet 2 (200 ppm), Diet 3 (400 ppm). The total experimental period was 56 days, with the first 7 days as diet adaptation to the Control diet prior to baseline collections. Total fecal collection was performed on days 10-14 and days 31-35, while fresh fecal samples were collected on days 0, 14, 21, 35, and 49. An antibiotic challenge was performed on days 14-21. Food was given once per day to maintain body weight and body condition score. A quadratic effect was observed for ATTD of dry matter (DM), organic matter (OM), total dietary fiber (TDF), and gross energy (GE). Dogs fed Diet 1 had the highest digestibility in DM, OM, TDF, and GE (P < 0.03) compared with other treatments before the antibiotic challenge. In addition, Diet 1 and Diet 2 had the highest OM and TDF digestibility (P < 0.009) compared with other treatments considering pre and post-antibiotic challenge measurements. Fecal score and pH did not differ among treatment groups (P >0.05). However, fecal metabolites differed among treatments. Indole was highest in the Control treatment (P=0.0047) with a linear contrast (P=0.0437), and 7-Methylindole and total indole was highest in Diet 1 (P < 0.05). There was also a quadratic effect of isovalerate (P=0.0373). Fecal calprotectin (CP) and IgA concentrations had a linear negative slope to increasing levels of herbal extract (P < 0.05). Alpha and beta-diversity (q < 0.05), as well the abundance of Fusobacteriaceae, Selenomonadaceae, Holdemanella, Na.17, and Blautia glucerasea in the fecal microbiota (P < 0.05), decreased in response to the antibiotic challenge (P < 0.05). In conclusion, this herbal extract mixture was well tolerated and accepted by dogs and had positive effects on nutrient digestibility and fecal metabolite concentrations.