The present invention relates to the use of Lactobacillus rhamnosus in combination with Bifidobacterium longum to manufacture a formulation to increase male fertility in a subject. In particular, said strains are the strains Lactobacillus rhamnosus CECT 8361 and Bifidobacterium longum CECT 7347. Additionally, the formulation comprising the said strains Lactobacillus rhamnosus CECT 8361 and Bifidobacterium longum CECT 7347 is also described.