Comparative effects of gelatin and hydrolysed gelatin from by-products as partial protein substitutes on canine health and gut microbiota

The search for sustainable protein sources in pet food is crucial for advancing the circular economy. Gelatin, a co-product of the pharmaceutical and leather industries, represents a promising and underutilised protein resource. This study investigated the effects of dietary gelatin or hydrolysed gelatin as partial protein substitutes on various health parameters, apparent total tract digestibility, and faecal bacterial microbiota in dogs. Twenty-four adult Labrador Retrievers were randomly assigned to one of three isonitrogenous and isocaloric diets: a control diet (CON), a diet containing 8% gelatin (G), or a diet containing 8% hydrolysed gelatin (GH). The 28-day trial involved monitoring BW, body condition score (BCS), faecal score, and feed intake. Blood samples were collected for haematological and biochemical analyses, and faecal samples were obtained for moisture content, apparent total tract digestibility, and faecal bacterial microbiota assessment. All diets were well-accepted, with no adverse effects observed on BW, BCS, faecal score, or blood parameters (P > 0.05), as all values remained within normal physiological ranges. However, the apparent total tract digestibility of DM, organic matter, and CP was significantly higher in the GH group compared to the G group (P < 0.05). Microbiota analysis revealed a significant reduction in Romboutsia timonensis and Clostridium disporicum in the GH groups compared to the CON group (P < 0.05). In conclusion, hydrolysed gelatin is a safe alternative protein source that can be incorporated into canine diets at a concentration of 8% without compromising their health. These findings support the use of hydrolysed gelatin as a sustainable and effective protein source in dog food formulations. However, the use of gelatin that has not undergone hydrolysis should be approached with caution due to its lower nutrient digestibility.