Published online by Cambridge University Press: 27 March 2009
1. An experiment was conducted to study the effects of progesterone and pregnant mare serum (p.m.s.) on incidence of oestrus, macroscopic changes in the ovaries, histological appearance of the genital tract, the vaginal smear and cervical mucus of New Zealand Romney Marsh ewes in deep anoestrus. Ten animals served as controls, thirty-five received progesterone daily for 4–12 days and ten were given p.m.s. alone. The remaining fifteen ewes were treated with progesterone for 4–6 days followed by p.m.s.
2. In ewes treated with progesterone alone, neither ovulation nor oestrus resulted. After p.m.s. alone six animals ovulated, while injection with both hormones caused ovulation in all 15 ewes and one was in oestrus.
3. Sections cut from the mid-region of the fallopian tube, uterine horn and cervix were examined. Histological responses to progesterone and p.m.s. were found in all positions of the tract and were greatest in the ewes which had ovulated.
4. In the ewes which ovulated a sequence of macroscopic and microscopic changes occurred in the vagina and these seemed similar to those associated with ovulation during the oestrous cycle.
5. Crystallization patterns in cervical mucus were seen in some ewes of all groups. Accompanying ovulation the phenomenon was seen for several days but was absent during most of the luteal period. When no follicles ruptured cervical mucus patterns often persisted. In most cases the presence and absence of arborization was presumably related to follicular oestrogen and progesterone from an induced corpus luteum and was in similar time relationship to that normally accompanying ovulation in the oestrous cycle. Some inconsistency in the response of cervical mucus following hormone treatment was noted.
6. No evidence was found that hormone treatment had initiated a regular cycle of ovarian activity.