POSSIBLE INFLUENCE OF THE BULL ON THE INCIDENCE OF EMBRYONIC MORTALITY IN CATTLE

Milk progesterone profiles were used to study the high incidence of embryonic mortality between 30 to 80 days after insemination in 91 cows in a single herd. The progesterone levels dropped to basal values at 46.7 +/- 1.37 days after service in 22 per cent of apparently pregnant cows. Embryo loss occurred significantly more frequently following services by one bull (Z). The mortality rates were 14/32 (44 per cent) in cows conceiving to Z compared with 8/73 (11 per cent) in cows conceiving to other bulls. There was no significant effect of the age of the cow or yield on the incidence of embryonic mortality.