estrous cycles were observed and concentrations of progesterone were measured after abortion in crossbred angus heifers that were injected with a prostaglandin f ( 2 ) alpha analogue about day 50 ( 15 heifers ) , 75 ( 14 heifers ) , 100 ( 13 heifers ) or 125 ( 49 heifers ) of gestation .
C0033308
progesterone
C0032961
gestation