There is growing interest in alternative protein sources to promote a more circular economy within agri-food systems. This study evaluated the impact of replacing 7% of poultry meal (PM) with hydrolysed feather meal (HFM) in canine diet on faecal characteristics. Six adult female English Setter dogs, matched for age, body weight, and body condition score (BCS), were divided into two groups and tested with two diets (PM vs. HFM) in a cross-over design. The study included a 7-d adaptation period, followed by a 45-d total faecal collection. A 30-d washout period was used. Digestive fermentation by-products were analysed by using gas and liquid chromatography. Data were analysed using a generalised linear mixed model (GLMM), with diet, time and their interaction as fixed effects, and the experimental phase as a random effect. Faecal scores for both groups remained within the range of 2–3, which is considered ‘ideal’. Dogs fed the HFM diet showed significantly higher (p < 0.001) faecal concentrations of acetate and isobutyrate, and significantly lower (p < 0.01) levels of propionate and butyrate compared to the PM diet. Furthermore, dogs fed HFM diet exhibited significantly increased (p < 0.001) concentrations of putrescine and cadaverine and significantly decreased (p < 0.001) levels of spermine. The profile of short-chain fatty acids (SCFAs) and biogenic amines differed from that those reported in dogs with inflammatory enteropathies, confirming the maintenance of gastrointestinal health throughout the study. These results suggest that HFM is a promising alternative protein source for dog food formulations, contributing to the sustainable utilisation of animal by-products.
