Negative effects on gut health have been reported in dogs fed meat-based diets; however, these diets were often higher in crude protein (CP) content.
To differentiate the effects of protein level and protein source on specific indicators of gut health in dogs.
Six experimental extruded diets were fed to dogs (n = 8). Meat-based and meat-free diets were compared at three levels of CP (16%, 24% and 32%). Using a 2-period cross-over design, both the meat-based and the meat-free diet of the same CP level were tested in each dog. The primary source of protein was maize gluten and soy meal in the meat-free diets, and poultry meal in the meat-based diets. All diets met AAFCO nutrient requirements.
Faecal concentrations of branched-chain fatty acids increased (P < 0.05) whilst Lactobacillus counts decreased (P < 0.05) as dietary CP levels increased (R2 = 0.10). Faecal amines increased (P < 0.01) with increasing CP levels (R2 = 0.38) for the meat-based diets only.
Increasing dietary CP intake had a negative effect on the markers of intestinal health measured in our experiment, whereas source of protein had no significant effect. Diets of higher CP content are intended for dogs with higher CP requirements (e.g., growing and exercising dogs). It is important to feed dogs diets designed for their specific needs, as CP ingested in excess of requirements may have a negative effect on animal health.