Ainsworth L, Lachance R, Labrie F
J Anim Sci. 1982 May;54(5):998-1004. doi: 10.2527/jas1982.545998x.
In two experiments, 64 crossbred ewes that had lambed in September or January and had their lambs removed within 24 h after birth were assigned to four groups and given the following treatments: group 1 (16 ewes)-1 ml saline, im or iv on d 10 postpartum; group 2 (24 ewes)-150 microgram/gonadotropin releasing hormone (GnRH) in 1 ml saline, im or iv on d 10 postpartum; group 3 (16 ewes)-150 microgram/GnRH in 1 ml saline, im or iv on d 10 postpartum, plus 40 mg fluorogestone acetate (FGA)-impregnated intravaginal sponges for 12 d beginning 22 d postpartum and group 4 (eight ewes)-40 mg FGA-impregnated intravaginal sponges only for 12 d beginning 22 d postpartum. Pregnant mare's serum gonadotropin (500 IU) was injected im into FGA-treated ewes at the time of sponge removal. Blood samples were collected from eight ewes in groups 1 and 2 at regular intervals up to 2 and 6 h, respectively, after treatment and analysed for luteinizing hormone (LH). Plasma progesterone (P) levels in blood collected once or twice weekly were used to monitor ovarian activity. GnRH induced a release of LH in all ewes monitored, whereas the LH levels remained unchanged in saline-treated ewes. Only 44% of the latter ewes had shown evidence of luteal activity by 50 d postpartum. The mean plasma P levels in the GnRH-treated ewes did not rise above basal preinjection values during the 14 d after treatment. In contrast, a synchronized ovulation followed by normal luteal activity was induced in 88% of the FGA-sponge-treated ewes. Of 16 ewes from group 2 slaughtered 26 d postpartum, 13 had ovaries that contained luteinized structures and uterine involution was incomplete in six ewes. These results preclude the use of GnRH as a single injection for induction of cyclic ovarian activity in the early postpartum ewe and indicate the need for progestogen treatment to initiate cyclic ovarian activity by 35 d postpartum. However, incomplete uterine involution may limit the number of ewes that can be successfully rebred at this time.
在两项实验中，将64只在9月或1月产羔且产后24小时内羔羊被带走的杂交母羊分为四组，并给予以下处理：第1组（16只母羊）——产后第10天肌肉注射或静脉注射1毫升生理盐水；第2组（24只母羊）——产后第10天肌肉注射或静脉注射1毫升含150微克促性腺激素释放激素（GnRH）的生理盐水；第3组（16只母羊）——产后第10天肌肉注射或静脉注射1毫升含150微克GnRH的生理盐水，并且从产后第22天开始放置含40毫克醋酸氟孕酮（FGA）的阴道海绵12天；第4组（8只母羊）——仅从产后第22天开始放置含40毫克FGA的阴道海绵12天。在取出海绵时，给接受FGA处理的母羊肌肉注射500国际单位的孕马血清促性腺激素（PMSG）。在处理后分别在2小时和6小时内，从第1组和第2组的8只母羊中定期采集血样，并分析其中促黄体生成素（LH）的含量。每周采集一次或两次血液样本，检测血浆孕酮（P）水平，以监测卵巢活动。GnRH可使所有监测的母羊释放LH，而生理盐水处理的母羊LH水平保持不变。到产后50天时，后一组母羊中只有44%显示有黄体活动迹象。GnRH处理的母羊在处理后的14天内，血浆P的平均水平未超过注射前的基础值。相反，88%接受FGA海绵处理的母羊诱导出现同步排卵并伴有正常的黄体活动。产后26天屠宰的第2组的16只母羊中，13只母羊的卵巢含有黄体化结构，6只母羊子宫复旧不完全。这些结果排除了将GnRH单次注射用于诱导产后早期母羊周期性卵巢活动的可能性，并表明需要进行孕激素处理以在产后35天前启动周期性卵巢活动。然而，子宫复旧不完全可能会限制此时能够成功再次配种的母羊数量。
