Apparent and True Digestibility of Minerals in Animal and Vegetable Ingredient Based Adult Maintenance Dog Food

Minerals are essential in the diet of dogs throughout all life stages. There is dearth of knowledge with regards to mineral digestibility in canines, and current knowledge focuses on the digestibility of supplemented minerals, not of endogenous mineral bioavailability of ingredients or formulated diets. The objective of this study was to determine the apparent digestibility and true digestibility of macro and trace minerals in canines fed either animal or vegetable based adult maintenance diets. We hypothesized that dogs fed the animal ingredient based diet would have higher mineral digestibility as compared to dogs fed the vegetable ingredient based diet. This study was designed as a 4 x 4 replicated latin square. Eight purpose bred Beagles (2 intact males, 6 spayed females) of similar age (2.12 ± 0.35 years) were pair housed, but fed individually based on individual energy requirements. Four diets (animal ingredient based diet, vegetable ingredient based diet, animal ingredient based diet diluted to 50% a-d-glucose, and vegetable ingredient based diet diluted to 50% with a - d- glucose) were fed to dogs with titanium dioxide included in the diet at 0.3% to enable calculation of digestibility. Kennel numbers were randomly assigned to each pair of dogs with all 8 dogs cycling through the 4 trial diets in random order. Each diet was fed for 10 d and fecal samples were collected from d 6-10. Data were analyzed using a mixed model through SAS (version. 9.4, SAS Institute) with treatment, period, and kennel as a fixed effect and dog as the random effect. There was no difference in apparent digestibility of calcium between dogs fed vegetable vs. animal diets; however, dogs fed the vegetable based diet had greater true digestibility of calcium (p=0.0143) as compared to dogs fed the animal based diet. The apparent and true digestibility phosphorus and iron were greater in dogs fed the vegetable based diets as compared to animal based diets (p<0.001). There were no differences in apparent or true digestibility of potassium, copper, and zinc between dogs fed the animal and vegetable based diets (p>0.05). These results suggest that apparent and true digestibility do not result in similar conclusions, and digestibility of endogenous minerals are similar, or greater in dogs fed diets that are largely vegetable based.