The effects of galacto-oligosaccharides on faecal parameters in healthy dogs and cats

The aim of this study was to evaluate the effects of galacto-oligosaccharides (GOS) on faecal parameters in healthy dogs and cats. To this end, 20 dogs and 20 Domestic shorthair cats were fed a commercially available adult dog food, or cat food, respectively, with either syrup containing GOS (at 1% w galacto-oligosaccharides/w formulated feed) on top (test group) or no topping (control group) for 56 days in a cross-over design. The study consisted of 2 periods of 24 days adaptation, followed by 4 days of collection of faeces. Faecal samples were tested for moisture, nitrogen, pH, macronutrients, enzymes, and fermentation products. The faecal microbiota were analysed by 16S rDNA profiling. It appeared that GOS have different effects in dogs compared to cats. In dogs, the addition of GOS resulted in increased carbohydrate fermentation (increase of acetic and butyric acid), whereas in cats GOS resulted in increased amino acid fermentation (increase of isovaleric acid). The alpha-diversity of the canine faecal microbiota was reduced by dietary GOS (Inverse Simpson Index, p = 0.063; Shannon index, p = 0.035) whereas the alpha-diversity of cat faecal microbiota was unaffected (Inverse Simpson Index, p = 0.539; Shannon index, p = 0.872). Lachnospiraceae spp. and Bifidobacterium spp. positively responded to GOS in both cats and dogs. Lactobacillus spp. and Enterobacteriaceae spp. positively responded to GOS in dogs. In both dogs and cats, GOS may therefore improve stool microbiota and result in the production of specific metabolites that are beneficial to gut health.