Macroalgae and microalga blend in dogs' food: Effects on palatability, digestibility, and fecal metabolites and microbiota

The promotion of dogs' nutrition, health, and well-being are highly valued by pet owners, leading to an increasing interest in pet food with alternative, functional, and more sustainable supplements, such as algae. Few studies have assessed the supplementation of dog food with individual algae species, but no information exists on combined macro- and microalgae. This study evaluated the effects of dietary supplementation of a commercial algal blend, composed of two macroalgae (Ulva rigida and Fucus vesiculosus) and one microalga (Chlorella vulgaris) on palatability, intake, digestibility, metabolizable energy (ME), and fecal characteristics, metabolites, and microbiota of adult healthy Beagle dogs. Palatability was assessed by comparing a complete diet without (control) and with 1.5 % algae blend using twelve dogs. Then, six of these dogs were randomly selected for the digestibility trials. Following an initial trial to determine the control diet digestibility, a replicated Latin square was performed with three experimental periods of 10 days each, and three algal blend supplementation levels (0.5, 1.0, and 1.5 %). Dietary algal blend did not affect the first approach and first taste, but dogs preferred the control diet. Algal blend levels had no impact on intake, but organic matter, fiber, and energy digestibility increased with 1.5 % inclusion compared with 0.5 %. At the highest level, algae blend promoted fecal total short chain fatty acids and acetate while at lowest fecal propionate decreased and fecal production increased. Compared with the control diet, algal blend-supplemented diets promoted most nutrients and energy digestibility, diet ME content, and fecal quality, while reducing fecal butyrate. Fecal microbiota diversity and abundance were mostly unaffected by algae blend supplementation, with health-promoting genera Turicibacter and Blautia being the most abundant in all samples. Overall, results suggest algal blend as a promising alternative supplement for dog food, but further research is needed to unveil potential health-promoting effects.