In vitro effect of diets added with fructooligosaccharides and differing in their protein content and digestibility on dog fecal microbiota

Abstract Text: Feeding dogs with diets containing high amounts of low-digestible protein may negatively affect the animal intestinal ecosystem, increasing the presence of undesired proteolytic bacteria. On the other hand, the administration of prebiotics can enhance the activity of beneficial bacteria residing in the canine intestine. The objective of the present study was to evaluate in vitro the effect of diets differing in their protein content and digestibility, and containing or not fructo-oligosaccharides (FOS), on canine fecal microbiota. There were 6 treatments: 1) Low-protein diet (LPHD, 23% CP); 2) High-protein diet (HPHD, 30% CP); 3) High-protein low-digestible diet (HPLD, 30% CP); 4) Diet 1 + 1.5% FOS (LPHD+FOS); 5) Diet 2 + 1.5% FOS (HPHD+FOS); 6) Diet 3 + 1.5% FOS (HPLD+FOS). After enzymatically digestion, the undigested fraction of the diets was added to a canine fecal suspension and  incubated for 24 h in an anaerobic cabinet (5 bottles per diet). From each bottle, a sample of fermentation fluid was collected at 6 and 24 h of fermentation for microbial counts (by FISH) and chemical analyses. Data were analyzed by three-way ANOVA, with protein level and digestibility and FOS as the main effects. At 24 h, FOS resulted in lower ammonia (36.4 vs. 40.3 mmol/l; P<0.001) and iso-valeric acid (0.52 vs. 1.44% of total volatile fatty acids (VFA); P<0.05) and higher total VFA concentrations (47.1 vs. 32.9 mmol/l; P<0.001). Conversely, LD diets resulted in lower VFA (33.9 vs. 43.1 mmol/l; P<0.001). The presence of FOS induced a shift in VFA production, reducing acetic acid (57.1 vs. 73.8%; P<0.001) and increasing propionic and n-butyric acids proportions (20.9 vs. 16.4% and 21.0 vs. 7.5%, respectively; P<0.001). With regard to biogenic amines, putrescine concentrations were increased at 6 and 24 h of fermentation by LD diets (+21 and 22%, respectively; P<0.05) and FOS (+18 and 24%, respectively; P<0.01). After 24 h of fermentation, HP diets resulted in lower counts of lactobacilli and enterococci (-0.5 and -0.7 log cells/ml, respectively; P<0.05) whereas LD diets tended to increase counts of C. perfringens (+ 0.2 log cells/ml; P=0.07). Results from the present study showed that diets rich in low-digestible protein may exert a negative influence on the canine intestinal ecosystem, increasing the presence of proteolytic compounds and reducing counts of beneficial bacteria. Conversely, administration of FOS may improve canine intestinal health, reducing proteolysis and enhancing VFA production.

Keywords: Dogs, Fructo-oligoccharides, Dietary protein