[en] Post partum anoestrus ; Dairy cows ; Beef cows
[fr] Anoestrus post partum ; Vaches laitières ; Vaches viandeuses
[en] The authors give a survey of the actual knowledge about the fundamental endocrinology of the ovarian cycle in the bovine. In an experiment using 5 dry cows, 20 cows milked twice daily, and 5 freely suckled cows, a comparative study was made about the post partum ovarian activity by checking heat, by rectal palpation, and by analysis of daily blood and milk samples for ovarian steroids and gonadotropins. For the 3 groups of cows, the first postpartum ovulation was noted at respectively 23, 45, 115 days after parturition. Originally it was thought that a hypersecretion of prolactin was responsible, but no effect could be observed after administration of the prolactin-inhibitor bromocryptine. More recent experimental studies have shown that milking and especially suckling acts as a stess factor, provoking an increased secretion and release of corticosteroids and a decreased blood level of LH, largely responsible for the prolonged post-partum anoestrus period. The logical treatment is weaning, but this technique is often economically difficult to apply in beef cattle. The most indicated alternative treatment to speed up the first postpartum oestrus is the use of the vaginal coil (PRID) containing 2-3 g of progesterone and carrying a capsule with 10 mg of oestradiolbenzoate. The latter stimulates the resorption of progesterone. The coil was removed after 12 days and 500 IU of PMSG were injected. In anoestrous beef cattle, an ovulatory oestrus was induced with a conception rate of 45%.
Laboratoire d'Endocrinologie et de Physiologie de la Reproduction animale