THE EFFECT OF PROGESTERONE AND OESTROGEN ON ARBORIZATION OF CERVICAL MUCUS IN THE SPAYED EWE

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Abstract
SUMMARY: Three series of experiments were conducted with ovariectomized Romney ewes to determine the requirements of oestradiol benzoate (ODB) for oestrus, characteristic vaginal smear changes, and crystallization (arborization) of cervical mucus, when preceded by 3 days of progesterone treatment (10 mg/day). The respective values for ED50 of ODB (in μg) for oestrus, vaginal smear changes and arborization of cervical mucus, with the associated 95% fiducial limits, were 26·5–23·4–20·9, 15·4–13·2–11·8 and 12·2–7·0–5·2. In the second series of experiments, conducted during November and December, the oestrous response was negligible. During the experimental period February to May, when the first and third series of trials were performed, a greater and more consistent response was noted. The possibility of a seasonal effect in the spayed ewe is discussed. The use of vaginal smears and arborization of cervical mucus in quantitative studies with progesterone and oestrogen was considered. Comparison of cervical mucus and vaginal smears collected from ewes treated with a dose of 10 μg ODB showed more distinctive changes in the cervical mucus and easier classification of a response to oestrogen. The difficulty of collecting a satisfactory sample of cervical mucus is discussed.