Milk may help prevent potentially dangerous bacteria from being killed by the antibiotics used to treat animals.

Bacteria sometimes form structures called biofilms that protect them against antibiotics. One of the most important micro-organisms that causes mastitis in cows and sheep, called Staphylococcus, can evade veterinary medicines by forming these protective biofilms. Mastitis causes risks for public health if people drink infected milk and is expensive for farmers as it usually causes severe milk production losses and increased treatment costs.

Milk may protect these bacteria against low concentrations of antibiotics. In the presence of milk, three out of five antibiotics tested became less effective against Staphylococcus.