Liquid Hydrolyzed Fish Protein (Anchovy) in the Canine Diet: A Focus on Gut Fermentation and Fecal Quality

Hydrolyzed protein is increasingly used in pet food, especially for animals with adverse reactions to food or gastrointestinal issues. This randomized, double-blind controlled trial evaluated the effects of a diet containing hydrolyzed anchovy protein on the gut health of healthy adult West Highland white terriers (5 males, 25 females; 5.6–9 kg). The dogs were randomly assigned to a control group (CTR, n = 15), receiving a standard commercial diet, or a treatment group (TRT, n = 15), fed a diet partially replacing anchovy meal with hydrolyzed anchovy protein for 42 days. All the dogs underwent a veterinary health check at baseline (T0) and remained healthy throughout the study. The food and water intake were recorded daily. The body weight (BW), body condition score (BCS, 1–9), and fecal score (FS, 1–7) were assessed at days 0, 21, and 42. Fecal samples were collected at T0 and T42 to measure calprotectin, cortisol, and putrefactive compounds (indole and skatole). No significant differences were found between the groups in the BW, BCS, FS, calprotectin, or cortisol. However, the TRT group showed a significant reduction in fecal indole and skatole. The results suggest that hydrolyzed anchovy protein may improve gut fermentation and support better digestive health in dogs, leading to reduced fecal odor and increased owner satisfaction.