Journal of Dairy Research

Original articles

Oxygen concentration in milk of healthy and mastitic cows and implications of low oxygen tension for the killing of Staphylococcus aureus by bovine neutrophils

Susan J. Mayera1, Avril E. Watermana2, Peter M. Keena3, Neil Cravena4 and F. John Bournea1

a1 Departments of Veterinary Medicine, Langford, Bristol BS18 7DU, UK

a2 Departments of Veterinary Surgery, Langford, Bristol BS18 7DU, UK

a3 Departments of Pharmacology, University of Bristol Veterinary School, Langford, Bristol BS18 7DU, UK

a4 Monsanto plc, Basingstoke, Hants, UK

Summary

The partial pressure of O2 in milk from normal cows and from cows with mastitis was measured and the concentrations of O2 calculated. Oxygen levels of milk from normal cows were similar to those in venous plasma, but inflammation of the mammary gland led to a dramatic drop in O2 concentration to < 10% of control values. Intracellular survival of Staphylococcus aureus strain M60 in bovine neutrophils was greater under anaerobic than aerobic conditions. The implications of low O2 concentrations in milk from infected mammary glands for the bactericidal activity of bovine neutrophils is discussed.

(Received August 18 1987)

(Accepted April 19 1988)