Lofstedt R M, Patel J H
Department of Medicine, School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.
J Am Vet Med Assoc. 1989 Feb 1;194(3):361-4.
In our experience, altrenogest has not always been able to exert predictable control over the estrous cycle of the mare. Therefore, we examined 12 mares that were treated with altrenogest to identify reasons for its failure to control the estrous cycle. The mares were fed altrenogest for 15 to 20 days and were examined for follicle development, ovulation, and corpus luteum formation during treatment. Through the use of real-time ultrasonography and radioimmunoassay for progesterone, we concluded that altrenogest was unable to suppress the growth of follicles to preovulatory size in some mares, leading to ovulation during treatment or earlier than expected after the end of treatment. In addition, altrenogest did not appear to shorten the life-spans of the corpora lutea that were formed during treatment; in 4 mares, this resulted in the persistence of corpora lutea after the end of the suggested 15-day periods of treatment. The latter findings led us to suggest that if a luteolytic dose of prostaglandin had been given at the end of altrenogest treatment, there would have been improved control over the estrous cycle. The results of our study confirmed our clinical impressions that altrenogest may be satisfactory to control the equine estrous cycle under some circumstances, but it should not be used when precise control over ovulation is required.
根据我们的经验，烯丙孕素并非总能对母马的发情周期发挥可预测的控制作用。因此，我们检查了12匹接受烯丙孕素治疗的母马，以确定其未能控制发情周期的原因。给这些母马投喂烯丙孕素15至20天，并在治疗期间检查卵泡发育、排卵和黄体形成情况。通过使用实时超声检查和孕酮放射免疫测定法，我们得出结论，在一些母马中，烯丙孕素无法将卵泡生长抑制到排卵前大小，导致在治疗期间排卵或在治疗结束后比预期更早排卵。此外，烯丙孕素似乎并未缩短治疗期间形成的黄体寿命；在4匹母马中，这导致在建议的15天治疗期结束后黄体持续存在。后一项发现使我们认为，如果在烯丙孕素治疗结束时给予溶黄体剂量的前列腺素，对发情周期的控制会得到改善。我们的研究结果证实了我们的临床印象，即烯丙孕素在某些情况下可能足以控制马的发情周期，但在需要精确控制排卵时不应使用。
