**6.4 Mesenchymal stem cells (MSCs)**

Although many methods are effective against bovine mastitis, they do not address the problem of udder tissue regeneration and are associated with increased antibiotic resistance worldwide. Experimentally gold in terms of the safety and efficacy of staphylococcus, given the need for alternative therapies that have a large economic impact on the disease, and reports of mesenchymal stem cell (MSC) regeneration and antibacterial effects. We evaluated this intramammary therapy based on color-induced allogeneic MSCs. In a safety study, heifers received a 2.5 x 107 AT-MSCs on day 1 and 10. The animals are clinically examined and blood samples were taken for testing. In efficacy studies, Holstein black-and-white cows were vaccinated with *Staphylococcus aureus*, carrier (NEG; days 4 and 10), antibiotics (ATB; days 4 and 5), or 2.5 x 107 AT-. MSC (MSC; 4th and 5th day). Cows are clinically examined daily and somatic cell count (SCC) and colony forming units (CFU) are collected from milk samples. Blood samples are collected to measure serum haptoglobin and amyloid A. Two intra-mammary injections of AT-MSC into healthy dairy animals do not cause changes in clinical or hematological parameters, and pro-inflammatory cytokines. Compared to a quarter of the ATB or NEG infected cows, a quarter of the cows in the MSC group had a similar log/ ml SCC of milk. However, compared to a quarter of NEG cows, a quarter of MSC cows have a lower log CFU/ml. Re-inoculation with 2.5 x 10 allogeneic AT-MSC in the udder does not elicit a clinical or immune response in healthy cows. In addition, anti-inflammatory treatment with MSC reduced the number of bacteria in the milk of cows with clinical *Staphylococcus aureus* mastitis compared with untreated cows. This study provides preliminary evidence for the safety and efficacy of emulsions based on allogeneic intra-mammary MSCs for the treatment of bovine mastitis [61].
