Effect of chronic treatment with bromocryptine on the corpus luteum function of the cow

Six heifers received an intramuscular injection of 15 mg bromocryptine twice daily from day 1 (the day of standing oestrus was defined as day 0) until 50 h after the start of luteal regression. The overall mean level of prolactin was 0.22 ±0.01 μg/l (SEM; n=6) in the bromocryptine-treated group and 10.7±2.7 μg/1 (SEM; n=6) in the control group. No significant differences in the overall mean level of progesterone and LH, the mean length of the early-luteal phase, the luteal phase and the period of luteal regression were measured between the two groups. The results provide strong evidence that prolactin has no luteotrophic properties in the cow during the oestrous cycle.