303 Apparent total tract digestibility of various protein sources in Beagle dogs at different life stages.

Abstract This study was conducted to evaluate the apparent total tract digestibility (ATTD) of various protein sources in Beagle dogs at different life stages. A total of 6 experimental diets were formulated using different protein sources including beef meal (BM), black soldier fly larvae (BSFL, Hermetia illucens), mealworm (MW, Tenebrio molitor), dried pollock (DP), isolated soy protein (SP), and chicken breast meal (CM), with similar crude protein (CP) and metabolizable energy (ME) levels. The Beagle dogs used in this study were classified into three groups: puppies (under 12 months; 4 spayed females, 4 neutered males), adult dogs (4 years old; 8 spayed females), and senior dogs (10 years old; 5 spayed females). After a 7-day adaptation period, ATTD was evaluated over a 4-day period using the total fecal collection method. The chemical composition of the diets and feces was analyzed according to AOAC standard methods. The Kruskal-Wallis test was used to analyze differences among life-stage groups, followed by Dunn’s post-hoc test for significant variables. Dry matter (DM) digestibility did not show significant differences among life stages. However, the digestibility of nitrogen-free extract (NFE) was significantly lower in puppies than in adult dogs for BSFL (P < 0.05) and SP diets (P < 0.01). CP digestibility varied depending on the protein source and life stage. Specifically, in the pooled digestibility analysis, when age-related differences were examined independent of protein source, puppies showed lower digestibility compared to adult and senior dogs. This trend was also observed in amino acid (AA) digestibility, with significantly lower digestibility of isoleucine and histidine (P < 0.05), as well as lysine and arginine (P < 0.01). Ether extract (EE) digestibility varied depending on the protein source, with puppies exhibiting higher fat digestibility than adult dogs in the pooled analysis (P < 0.05). Calcium (Ca) digestibility varied depending on both protein source and life stage, with puppies showing lower digestibility for the CM and DP diets (P < 0.01), but higher digestibility for the MW diets compared to adults and senior dogs (P < 0.001). When age-related differences were examined independent of protein source, phosphorus digestibility was lower in puppies than in adult dogs (P < 0.05). These findings suggest the necessity of precise nutrient composition adjustments based on life stage, providing fundamental data to support such considerations. This study compared the life stage-specific utilization of alternative protein sources with conventional livestock-derived proteins commonly used in dog food. These findings provide scientific evidence on nutrient utilization across life stages in dogs. Furthermore, these findings highlight the practical potential of alternative protein sources in dog nutrition and their contribution to the development of optimized feeding strategies.