Most of the veterinary treatments available are either hormonal or surgical. In terms of hormonal treatment, Regumate, which contains a progestagen, is used by vets to assess whether the sex hormones are to blame for the reported behavioural problems.

Short courses of the drug will provide information but the behaviour is likely to return shortly after the drug is discontinued. Some use it long term but it is not licensed for use in this way and is very expensive.

A more drastic approach, which some owners take as a last resort, is to have the mare’s ovaries removed. This procedure can be performed standing, but is not without risk, including development of signs of recurrent colic following abdominal infection (peritonitis).

Removal of the ovaries is unlikely to change the mare’s behaviour if Regumate hasn’t worked.

Supplements currently available for changing a mare’s behaviour include Frisky Mare, Hormonise, Hormonal Mare, Relax Her Mare, Mare Magic, Moody Mare, Stroppy Mare and Oestress – some of these are veterinary approved.

They contain a variety of herbal products including valerian, Ltryptophan, camomile, devil’s claw, poppy, St John’s wort and raspberries.

There is little scientific evidence available for any of these supplements working in horses. However, there is evidence in humans that the individual components may help hormone-related problems.

Valerian is a sedative and calmer, camomile and devil’s claw are antiinflammatory and antispasmodic, so may help those mares with mild pain. Poppy has pain-relieving properties and is a sedative, St John’s wort and L-tryptophan are effective antidepressants.

Care must be taken in the use of these products in competing mares as they may contain banned substances (such as valerian).

Some vets are advocating placing marbles in the womb of difficult mares. The idea behind this is that the mare’s body may think she’s pregnant
and may supress seasons and, therefore, the difficult behaviour.

There is no scientific evidence that this treatment actually helps difficult mares but it’s worth discussing this option with your vet if all other treatments have failed – and it’s certainly less drastic than having the ovaries removed.

It’s not without risk, though – putting any foreign body inside an animal increases the risk of infection and this could affect future fertility.