Some mares are difficult to manage and perform poorly as a result. They may be uncooperative or aggressive when handled on the ground. They may kick, buck or rear when ridden or may be aggressive towards other horses.
Unwanted behaviour may result from pain from orthopaedic or other sources. Sometimes it is related to the mare coming in season, in which case it may be improved by suppressing the oestrus cycle.
Some ovarian tumours, although less common, may produce similar effects. Treatment of these cases is likely to involve removing the affected ovary (ovariectomy).
But sometimes there is no obvious explanation for the unwanted behaviour. Would removing both ovaries (bilateral ovariectomy) help?
A study by Daniel Taasti Melgaard, of the Horsholm Equine Clinic, Fredensborg, Denmarkand colleagues looked at whether removing the ovaries from mares with unexplained unwanted behaviour improved the mare’s behaviour or rideability.
Twenty-eight mares underwent surgical removal of both ovaries once the clinicians had ruled out painful causes and after the mares had not responded to a trial period of hormone therapy to suppress oestrus behaviour.
Owners reported that, after bilateral ovariectomy, 80% (8/10) of mares with normal ovaries and 57% (8/14) of mares with ovarian neoplasia were easier to ride. Behaviour was reported to be better in 40% (4/10) of mares with normal ovaries, and in 43% (6/14) of mares with ovarian neoplasia.
A full, open access, report is published in the journal Animals.
The authors emphasise the importance of a thorough diagnostic work up to rule out other conditions, such as orthopaedic, alimentary, vaginal or uterine pathology, before considering ovariectomy for unwanted behaviour.
They suggest that, despite the significant improvement observed in the present study, further research is necessary to confirm whether mares with unwanted behaviour not obviously related to the oestrus cycle and to painful conditions may benefit from ovariectomy to alter their behaviour and rideability.
“In conclusion”, they write, “a significant improvement was observed in rideability and behaviour post- ovariectomy, but no statistical difference in improvement after ovariectomy between mares with ovarian neoplasia and mares with histopathologic normal ovaries was observed. The results suggest that mares with and without neoplasia can equally benefit from ovariectomy to improve behaviour and rideability.”
For more details, see:
Daniel Taasti Melgaard, Trine Stokbro Korsgaard, Martin Soendergaard Thoefner, Morten Roenn Petersen, Hanne Gervi Pedersen.
Animals (Basel) (2020)