Autor: Luisa Vierbaum

"In vitro evaluation of the effects of Yucca schidigera and inulin on composition and metabolism of faecal microbiota of high- and low-protein fed dogs" This in vitro study aimed to evaluate the effects of Yucca schidigera powder (YSP) and inulin (I) on composition of faecal microbiota and its formation of protein fermentation metabolites (short (SCFA) and branched-chain fatty acids (BCFA), phenolic and indolic compounds, biogenic amines, ammonia and pH) by using faecal inocula from dogs fed either a low (A) or a high (B) protein diet (crude protein 201 or 377 g/kg as fed). Nine treatments for each diet were evaluated in an in vitro batch culture system over 24 h: (1) control with no addition of substrate; (2) 2,00 g/l YSP; (3) 4,00 g/l YSP; (4) 2,00 g/l YSP and 1,00 g/l I; (5) 4,00 g/l YSP and 1,00 g/l I; (6) 2,00 g/l YSP and 5,00 g/l I; (7) 4,00 g/l YSP und 5,00 g/l I; (8) 1,00 g/l I; (9) 5,00 g/l I of faecal culture of dogs fed diet A or B. Several changes in fermentation metabolites were analysed. Samples incubated with the faecal inocula of dogs fed diet B produced lower concentrations of total SCFA, acetate, propionate (p ≤ 0.001), i-valerate (p = 0.003), D-lactate (p = 0.041) and indole (p = 0.003), whereas pH (p ≤ 0.001) was increased. Supplementation of I increased the content of putrescine, D- and L-lactate, total SCFA, acetate, propionate, n-butyrate (p ≤ 0.001), while i-valerate, indole and pH (p ≤ 0.001) were reduced. Ammonia was lower (p ≤ 0.001) in samples with faecal inocula from dogs fed diet B and further reduced by the addition of I (p ≤ 0.001). Samples with faecal inocula from dogs fed diet A had a fewer quotient of ammonia and total SCFA (p = 0.003). Supplementation of YSP (p = 0.016), I (p ≤ 0.001), I in combination with diet A (p = 0.006) and YSP in combination with I (p = 0.031) led to a futher reduction of the quotient of ammonia and total SCFA. Total number of copies of all bacterial groups was increased in samples incubated with faecal inoculum from dogs fed diet A, the supplementation of I (p ≤ 0.001) and YSP (p = 0.021). Protein content of the diet as well as supplementation of I and YSP showed numerous positive effects on the abundance of the analysed bacteria. In conclusion, dietary protein concentration and the in vitro supplementation of I and YSP led to a stimulation of growth and fermentation intensity of the faecal microbiota, whereby YSP appeared to have only minor effects on the formation of protein fermentation metabolites.