Abstract: The present invention relates to the use of regenerative medicine in livestock farming, in particular to regenerative medicine for the care of livestock, and even more particularly to regenerative medicine in the care of milk-producing animals, including cattle. Specifically, the invention concerns a foetal mesenchymal stem cell (MSC) composition of allogenic origin, a treatment method and the use thereof in mastitis in milk-producing animals, including cattle, suffering from mastitis, to immunostimulate the animal, the MSC coming from foetal bovine adipose tissue. The composition can be administered via the intramammary route, exercising an immunomodulatory effect on the inflammatory response and strengthening antimicrobial activity against mastitis-causing pathogens in milk-producing animals with mastitis, thereby becoming an alternative to replacing and/or supplementing the use of antibiotics.