Peripheral blood concentrations of plasma steroids and a metabolite of prostaglandin F2 alpha in pregnant cows vaccinated against foot and mouth disease.

Blood samples were collected from 82 pregnant cows at 6-h intervals to determine the effects of vaccination against foot and mouth disease (FMD) on plasma concentrations of progesterone, total unconjugated oestrogens, total corticosteroids and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM). Twenty-two (26.8%) cows showed a strong post-vaccinal reaction in the form of a significant (P < 0.05) elevation in rectal temperature, accompanied by significant (P < 0.01) increases in plasma progesterone and corticosteroid concentrations for 36-42 h after vaccination. Seven (8.5%) cows returned to oestrus within 5-6 days when vaccinated during the first month of pregnancy and nine (10.9%) gave birth prematurely within 72-80 h when vaccinated during the last month of gestation. The importance of post-vaccinal reactions on embryonic mortality and premature birth is emphasized. It is suggested that cows in early and late pregnancy are most susceptible to adverse effects of vaccination against FMD.