[The role of prolactin during the estrus cycle of cattle]

Suppression of the prolactin level in the peripheral blood by chronic treatment with bromocryptin throughout the oestrous cycle of the cow, had no effect on: 1) LH concentrations during the cycle, 2) progesterone secretion of the corpus luteum, 3) duration of the early luteal phase, the luteal phase and the period of luteal regression, 4) oestradiol secretion during the follicular phase, 5) number and quality of follicles greater than 2 mm, 6) number of binding sites on granulosa cells and thecal tissue of the preovulatory follicle and 7) the concentration of oestradiol, androstenedione and progesterone in the follicular fluid of the preovulatory follicle. Follicles from bromocryptin treated and control heifers did not possess specific binding sites for prolactin. It is concluded that prolactin is not involved in the regulation of the oestrous cycle in cattle.