Detection of induced death of embryos in sheep by the rosette inhibition test

Summary.The rosette inhibition test has been used to monitor the decrease of an 'early pregnancy factor' in 2 groups of pregnant sheep (19–21 days) in which embryos were removed surgically or by induction of luteolysis with cloprostenol. The rosette inhibition titres of sera taken from sheep of each group declined from high (16–18) to low (8–10) levels within 48 h of treatment. Surgical removal of embryos caused little change in serum progesterone concentration whereas cloprostenol prompted a rapid decrease over the same period. Death of the embryo can therefore be detected by the rosette inhibition test within 48 h of occurrence, but not necessarily by the measurement of progesterone in blood within this period.