Ovarian fusion in sheep

A survey of ovine reproductive tracts was undertaken in 2 abattoirs in the south west of England, in which 23,536 tracts from nulliparous animals and 9970 tracts from cull ewes were examined. The ovaries were fused in 15 nulliparous animals. In 13 of these animals, 2 ovarian structures could be separately identified macroscopically, whilst in the 2 other animals, a single structure was seen. On histological examination of the ovaries in which 2 structures could be separately identified, the capsules were confluent and formed a septum between them. In the 2 cases with complete ovarian fusion, a narrow connective tissue septum separating the 2 ovaries was present. No cases of ovarian fusion were found amongst the cull ewes, but prominent strands of fibrous tissue connecting the ovaries were present in 2 animals. It is probable that fusion of the ovaries occurs as a developmental abnormality; evidence from the 2 cull ewes suggests that the ovaries separate once oestrous cyclicity has commenced.