Dietary strategies to support gut health in dogs: evaluation of dried bakery product and pine extract

Abstract

With the increasing “humanization” of pets, pet owners have become more aware of animal health and nutrition, and are increasingly prioritizing products that support the overall wellness of their companions. This trend has driven interest in functional pet foods, which are formulated to provide health benefits beyond basic nutrition. Among the many health aspects that pet food products may support, gastrointestinal (GI) tract health, or gut health, is of particular importance in companion animal nutrition. Gut health is defined as “a state of normal GI function without active GI disease or gut-related symptoms that affect quality of life”. The investigation of functional ingredients that support gut health in dogs is increasing. Notably, dried bakery product (DBP) and pine-derived extracts have emerged as novel options with strong potential to support gut health. Therefore, the objectives of this dissertation were to characterize the nutritional composition and physical properties of DBP (Chapter 2), evaluate its use in extruded dog diets and consumer acceptance (Chapter 3), and assess the potential gut health benefits of DBP when fed to healthy adult dogs (Chapter 4). Moreover, this dissertation also aimed to investigate the impact of a commercial pine essential oil (ArgaT) on gut health of healthy adult dogs (Chapter 5). To achieve those objectives, separate studies were conducted. The first study characterized the nutritional composition and physical properties of DBP samples collected from six manufacturing facilities across the United States. Nutrient composition was variable (P < 0.05) among locations, with dry matter (DM) ranging from 89.5 to 90.6%, crude protein from 9.4 to 13.6%, crude fat from 8.0 to 12.6%, total dietary fiber from 6.9 to 20.6% DM, and starch from 46 to 54% DM. Dried bakery product was considered a great source of starch, with most of the starch already being gelatinized (32 to 41% DM) and rapidly digestible (39.7 to 48.0% DM). One manufacturing facility in Texas produced DBP with particularly high concentrations of total and soluble dietary fiber; consequently, this source was selected for further investigation due to its potential relevance to gut health. The second study evaluated the effects of DBP inclusion in dry expanded dog food on physical properties, sensory attributes, and dog owner perception of the final products. Four diets were extruded containing 0%, 8.5%, 17%, and 25.5% DBP, which was added at the expense of rice, sorghum, and lentils. Increasing dietary inclusion of DBP decreased (P < 0.05) the sectional expansion index and increased (P < 0.05) specific length and piece density of kibbles. Trained panelists described diets containing 0% DBP as having a stronger aroma and presenting more intense beef and fishy aromas, which influenced consumer perceptions, as they preferred the aroma of diets containing DBP. Consumers also preferred the uniformity of shape and indicated higher overall liking for diets containing DBP. However, when asked about their opinion on DBP, only 6% of participants were familiar with the ingredient, and despite 49.5% believing that DBP was a sustainable ingredient, most participants (57.4%) did not believe DBP was a nutritious ingredient and 41.7% did not consider DBP to be safe for their dogs. In the third study, the same diets were offered to healthy adult dogs in a 4 x 4 Latin square design to assess the effects on fecal characteristics, microbiota, and metabolites. Inclusion of DBP in diets increased (P < 0.05) fecal output and DM, and reduced (P < 0.05) apparent total tract digestibility of DM, organic matter, crude protein, acid-hydrolyzed fat, and gross energy, but values remained >80% and fecal quality scores were not affected (P > 0.05). The dietary inclusion of DBP also influenced the fecal microbiota composition, including reductions (P<0.05) in Firmicutes and increases (P<0.05) in Fusobacteriota and Proteobacteria. Moreover, when included at more than 17%. DBP led to a decrease (P < 0.05) in molar concentrations of short-chain fatty acids, and negatively impact (P < 0.05) diet palatability. The last study evaluated the effects of ArgaT, a commercial product derived from pine trees containing terpenoids with antimicrobial and anti-inflammatory properties, on the gut health of dogs. Three dry expanded extruded diets were produced with 0%, 0.05%, and 0.15% ArgaT. Experimental diets were fed to 24 healthy Labrador Retrievers in a randomized complete block design. Dietary inclusion of ArgaT did not impact (P > 0.05) fecal dry matter, pH, calprotectin, IgA, or the dysbiosis index. The 0.15% inclusion resulted in a decrease (P < 0.05) in the abundance of five bacterial taxa (Faecalibacterium, Catenibacterium, Fusobacterium and unclassified Lachnospiraceae and Prevotellaceae). Despite these discrete taxonomic shifts, alpha and beta diversity remained stable (P > 0.05). Untargeted metabolomics identified 14 fecal metabolites modulated (q < 0.05) by diets containing ArgaT, including several carbohydrates (lactose, fructose, xylose) and organic acids. Notably, 11 of these metabolites were uniquely altered (q < 0.05) when dogs were fed the 0.05% ArgaT diet, suggesting that the lower inclusion level may have a greater impact on modulating microbial fermentation pathways. Overall, the results presented in this dissertation highlight the effects of two dietary strategies with on the gut health of healthy dogs. While DBP did not demonstrate an effect on gut health based on the parameters evaluated, this ingredient was still considered acceptable for inclusion in dry expanded dog food and represents a promising, sustainable ingredient for pet food formulations. In contrast, ArgaT demonstrated greater modulation of fecal microbiota and metabolites, and future studies should further evaluate the potential of ArgaT to support the gut health of dogs facing gastrointestinal issues.