Infertility in ewes caused by prolonged grazing on oestrogenic pastures: oestrus, fertilization and cervical mucus

Abstract

An experiment was conducted to investigate oestrus, fertilization and cervical mucus production in two groups of ewes, one group being of reduced fertility due to prolonged grazing on oestrogenic subterranean clover. Ewes within each of the oestrogenic (Yarloop subterranean clover) and control (Mt Barker subterranean clover) treatments were divided into subgroups of ‘high’ and ‘low’ fertility on the basis of total lambs born over the preceding 3 years. The results confirmed previous findings concerning a failure of sperm transport and reduced fertilization in affected ewes but the duration of oestrus (approx. 23 h) was normal. Ewes in the Yarloop treatment, and in particular those in the low-fertility subgroup, were found to produce significantly more cervical mucus than control ewes over the period - 30 to + 30 h relative to time of onset of oestrus. This result is discussed in relation to the failure of sperm transport. © 1974 ASEG.