EquineReview

The development of minimally invasive laparoscopic techniques has significantly reduced the rate of complications associated with ovariectomy in equids, allowing this procedure to be increasingly performed for the treatment of oestrus-related behavioural issues.

However, data are limited and there are conflicting opinions regarding the effects of bilateral ovariectomy on behaviour. A recent retrospective study by Collar et al (2021) investigated this in 51 mares. All mares undergoing bilateral ovariectomy over a 6-year period were included in the study and split into two groups: elective cases (n=41), where both ovaries were non-pathological, and non-elective cases (n=10), where hormone analysis and histopathology confirmed the presence of ovarian pathology (granulosa cell tumour 9/10 or arrhenoblastoma 1/10). As anticipated, rates of postoperative complications were low (8%) and were positively associated with the need for a hand-assisted ovariectomy technique. Of the 41 elective cases 90% (n=37) showed some improvement in the presenting behaviour, with 71% (n=29) showing complete resolution. Response to altrenogest (Regumate) was not an accurate predictor of the response to surgery. Oestrus-like behaviour was reported in 27% of cases after surgery, the reason for which remains unclear, but these signs were mild and generally manageable. Of the ten non-elective cases, all showed some improvement after surgery – with 90% showing complete resolution of undesirable behaviour. Limitations of the study included its retrospective nature, the owner-based follow up, the lack of a control group and the limited postoperative investigation of in the elective group.