[Studies of the course of the postpartum period in sheep of the Polish Merino breed. III. Progesterone level in the peripheral blood 1-40 days after labor].

Progesterone concentration was determined by RIA in 24 ewes of Polish Merino Breed on 1-40th day after parturition. In most of the studied ewes (58%) 1-3 luteal phases were observed. Elevated concentration of progesterone appeared on days 6-15, but in most cases on the 20th day postpartum approximately. Luteal phases of first oestrous cycles were shortened and lasted approximately 6 days, whereas normal length of oestrous cycles and progesterone concentration illustrating the presence of cyclic corpus luteum were observed on the 25th day after postpartum.