The effect of bromocriptine on luteinizing hormone levels in the lactating sow: evidence for a suppressive action by prolactin and the suckling stimulus.

Lactating sows (5 per group) were given no treatment or 10 mg bromocriptine orally twice daily from day 14 to 22 after parturition. Both groups were weaned at day 22. Frequent bleedings at 10 min intervals for 6 h were performed at 12, 16, 20 and 24 days after parturition. Prolactin and LH levels were measured in the collected blood samples by radioimmunoassays. Reduction of Prl by bromocriptine increased mean LH levels significantly and a further significant increase was observed after weaning. From the results it is concluded that in the lactating sow both Prl per se and the suckling stimulus are involved in suppression of LH levels.