Cervical mucus and reproductive efficiency in ewes after exposure to oestrogenic pastures

Abstract

A total of 227 cervical mucus samples was studied in ewes from 12 flocks with varying histories of clover disease, and the results related to the reproductive performance of the ewes. The mucus of ewes from flocks known to be affected with clover disease had a lower spinbarkheit than that of controls (54 v. 92 mm, P < 0.05). The spinbarkheit of cervical mucus at first mating was inversely correlated with the return-to-service rates of the ewes at subsequent matings (r = −0.181, P < 0.01). The low value of this correlation indicates that most of the variability in mucus spinbarkheit was due to other factors; the stage of the breeding season, and the total amount and the proportion of dry weight of the mucus collected, were also related to the mucus spinbarkheit.

Variability was decreased by adjusting the spinbarkheit for the time of the breeding season at which the sample was collected. There was a threshold value of 60 mm for mucus spinbarkheit, above which fertility was independent of mucus spinbarkheit value. The proportion of samples with sub-threshold spinbarkheit values collected from a flock was related both to flock return-toservice rate (r = 0.663, P < 0.05) and the proportion of non-lambing ewes in the flock (r = 0.605, P < 0.05). Neither mucus spinbarkheit nor the proportion of non-lambing ewes was associated with any abnormal increase in the proportion of ewes which failed to lamb in successive years.

It is concluded that cervical mucus spinbarkheit may be used to measure the lowered reproductive performance of ewes which have been exposed to oestrogenic pasture.