Endometrial change in the annual reproductive cycle of the mare

Cervical and endometrial swabs were taken from 7 mares at various stages of the oestrous cycle. There was no consistent pattern of cell change throughout the cycle. The dominant cell in smears from normal mares was the columnar epithelial cell, especially in smears obtained during oestrus. A ciliated columnar epithelial cell was found much less frequently but appeared more often in smears before oestrus. Endometrial biopsies were also collected from 7 mares at intervals 2-3 weeks over an 8-month period from the beginning of spring to the end of autumn. There was no obvious change in the endometrial histology during this time. No evidence of acute or chronic inflammatory change was found in sequential biopsies. The inflammatory response to a single endometrial biopsy and subsequent endometrial biopsies, as measured by exfoliative cytology 48 h after biopsy, was minimal. Bacteria were recovered after aerobic culture of cervical swabs on more occasions 48 h after than before uterine biopsy, but they were considered not to be significant.