Bactericidal activity of peripheral blood neutrophils during the oestrous cycle and early pregnancy in the mare

Abstract

The oestrous cycles of 20 mixed-breed mares were synchronized with daily injections of 10 mg oestradiol-17β and 150 mg progesterone given i.m. for 10 days. On the 10th day, 10-15 mg prostaglandin F-2α was administered i.m. to induce oestrus. Neutrophils were isolated from jugular blood on the 2nd or 3rd day of oestrus, Days 5 and 7 after ovulation or during early pregnancy (Days 18-34 of pregnancy). Neutrophils were challenged with Staphylococcus aureus and their bactericidal activity examined after 30 and 120 min of incubation for a reduction of colony forming units. Bactericidal activity increased with the time of incubation (P < 0.01) but did not differ for the oestrous cycle or pregnancy (P > 0.05).