Interpretive Summary: Apparent total-tract macronutrient digestibility, serum chemistry, urinalysis, and fecal characteristics, metabolites and microbiota of adult dogs fed extruded, mildly cooked, and raw diets
By: Megan LaFollette
In September 2018, Journal of Animal Science published an article that investigated the effects of feeding adult dogs different commercial diets with various processing levels. Most pet food diets use the process of extrusion to cook food with heat, moisture, and pressure. Extrusion is popular because it is an efficient, adaptable way to make highly digestible pet food with all essential dietary nutrients. Extruded food also has positive effects on stool quality. Despite this popularity, as pet owners grow even closer to their pets, they are becoming more interested in feeding their pets’ diets that seem more familiar to their own food, and appear to be more natural with functional ingredients. These novel pet foods may include raw or fresh foods that may or may not have grains. Unfortunately, there has been little research on these novel pet foods. The purpose of this study was to assess the effects of feeding adult dogs commercial diets with different levels of process on digestibility, fecal characteristics, microbiota, urinalysis, serum chemistry, and voluntary physical exercise.
In this study, 8 adult female beagles were fed four different commercially available diets: extruded dry, high-moisture roasted refrigerated, grain free high-moisture roasted refrigerated, and raw. Each individually housed dog ate all diets (with a 14-day adaptation phase during which diets were gradually changed from one to the other) so they could serve as their own control. The kibble was Nestle Purina brand while the other diets were Freshpet brand. It is important to note that each diet was very different in format and macronutrient composition (e.g. dry matter, fat, fiber, and energy density). The dogs were evaluated for physical activity using activity monitors for 7 days, fecal & urine collection for 5 days, and blood collection for 1 day.
Digestibility, fecal characteristics, microbiota and serum chemistry varied among the diets. For digestibility, greater apparent total-tract macronutrient digestibility was seen in the grain-free roasted and raw diets than the extruded diet. For fecal characteristics, the raw diet resulted in lower fecal pH and higher short-chain fatty acids (which are important for a variety of functions in the gut) than other diets. For microbiota, current diet impacted fecal microbiota type. The raw and grain-free roasted diets had reduced species richness than the extruded diet. For serum chemistry, all diets resulted in metabolite levels which were within normal levels and indicated good health. However, dogs had higher triglyceride and alkaline phosphatase concentrations when fed extruded diets than grain-free roasted or raw diets. The type of diet did not impact dog fecal scores, urine characteristics, or total voluntary physical activity.
Overall, it is important to note that the conclusions of this study are limited to differences of the diets as a whole – rather than simply the diets processing type. This limitation is because each diet contained different ingredients and concentrations of nutrients and energy, in addition to differences in processing. Therefore, the effects of processing cannot be separate from ingredients and nutrient concentrations. However, this study does show that dogs remained healthy and tolerated all four diets, including those that were lightly cooked and raw. All diets were highly digestible and maintained acceptable fecal quality and serum chemistry. Additionally, the lightly cooked and raw diets also were more digestible, reduced blood triglycerides and changed fecal microbial community in comparison to the extruded diet in this study.
To view the full article, visit the Journal of Animal Science.