Influence of Dietary Protein Content and Source on Fecal Quality and Protein-Derived Fermentation Products in Dogs Differing in Body Size
When given the same diet, large breed dogs produce feces of poorer quality than smaller ones due partially to higher fermentative activity in the hindgut. Undigested proteins are important substrates for fermentation by the colonic microflora. They can be metabolized to several bioactive products, which could have deleterious effects on the colonic mucosa. The aim of this study was to evaluate the effect of dietary protein source and amount on fecal quality and concentration of some key protein fermentation products in dogs differing in body size.
Twenty-seven female dogs of 6 different breeds (from 3.35 to 34.65 kg BW) were divided in 4 groups according to BW (miniature: MI, medium: ME and maxi: MA) and propensity to have softer feces (maxi tolerant: MT and maxi sensitive: MS). Five diets varying in protein source and level were tested in a 2-phase protocol consisting of a crossover and Latin square designs respectively. Diets were formulated to be isoenergetic and to have similar content of fat, TDF and ash. Main dietary protein sources and levels were as follows: wheat gluten meal in diets WGLP (CP=19.9%) and WGHP (CP=34.3%), mix of poultry and wheat gluten meal in diet WPMP (CP=26.2%), and poultry meal in diets PMLP (CP=19.3%) and PMHP (CP=35.2%). Feces were scored daily and fecal moisture was determined from a 7-day collection pool after a 7-day adaptation period. Fresh stools were collected (1-2 samples/dog and diet) and analyzed for ammonia and branched-chain fatty acids (BCFA). Data were statistically analyzed using ANOVA followed by Fisher's PLSD post hoc test.
Fecal quality was lower both with poultry meal diets (p<0.0001) and with high CP levels (p<0.01) whereas fecal moisture varied only with protein source (p<0.0001). Compared to MI dogs, MS dogs had a higher fecal moisture and a lower fecal quality on all diets (p<0.0001). Ammonia fecal concentration varied with dietary protein source (p<0.0001) and level (p<0.0001). Specially diet PMHP induced a significantly higher ammonia fecal concentration. MS dogs were particularly prone to have high ammonia concentrations (p<0.0001). BCFA varied both with protein source (p<0.001) and level (p<0.0001). An effect of dog size (p<0.01) was only observed on diets WGHP and WPMP.
Decreasing CP levels and introducing a source of highly digestible protein such as wheat gluten improves fecal score. Moreover it reduces protein fermentation in the hindgut. This is of interest to the overall hindgut health as ammonia production induces a faster cell turnover and modified intestinal cell's morphology and metabolism, affecting colonic absorption functions. According to our results these deleterious effects seem to be of higher importance in MS dogs.