Combination of microalgae <i>Phaeodactylum tricornutum</i> and <i>Nannochloropsis oculata</i> in the diet of dogs and its impact on animal health

The use of additives in pet food as an alternative to promote health has become increasingly common. Among these, microalgae, a natural source of polyunsaturated fatty acids and bioactive compounds, stand out. This study evaluated the effects of adding a 50:50 combination of Phaeodactylum tricornutum and Nannochloropsis oculata on the metabolism, antioxidant and immune responses, and gut microbiota of dogs. Ten male Beagles were divided into two groups: control (dehydrated natural diet) and treatment (the same diet with 0.5% of the microalgae combination). The experiment lasted 36 days, with blood and faeces collected for clinical and microbiological analyses. Dogs that consumed microalgae had higher lymphocyte counts, increased immunoglobulin A (IgA) and heavy-chain immunoglobulins, and higher high-density lipoprotein (HDL) and total cholesterol levels. There was a reduction in inflammatory markers (ceruloplasmin, ferritin, and amyloid protein), and an increase in transferrin when dogs consumed microalgae. There was an interaction between treatment and day for Thiobarbituric Acid Reactive Substances (TBARS) and reactive oxygen species levels (ROS), which were initially elevated, and subsequently reduced in the treated group. Although antioxidant enzymes were not altered, ferric reducing antioxidant power (FRAP) levels were higher in dogs fed microalgae. The gut microbiota was also modulated, with a reduction in pathogenic bacteria (Escherichia coli and Clostridium). These results indicate that adding microalgae to dogs’ diets promoted immunity, had antioxidant and anti-inflammatory effects, and contributed to intestinal health.