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polymethylmethacrylate (PMMA) sphere

Ultrasound view of an intra-uterine sphere

Intra-uterine spheres otherwise known as uterine balls or marbles for mares with undesirable behaviours are supplied by Equine Reproductive Services (UK) Ltd. Mares which are ‘mareish’ or show overt reproductive behaviours when they are in season are candidates for an intra-uterine sphere.

Intra-uterine spheres are devices which are thought to ‘mimic’ an early pregnancy and can cause the lifespan of the mare’s primary corpus luteum to be prolonged. The corpus luteum is the mare’s natural source of progesterone and if prolonged the mare may stay out of season for up to 90 days.

Historically such devices were glass marbles but we do not supply glass marbles. Glass marbles have been found to have broken in mares and have been known to be difficult to remove. Perhaps more importantly glass is microporous and has the potential to result in chronic infection or adhesion to the uterine lining. At Equine Reproductive Services (UK) we supply polymethylmethacrylate (PMMA) spheres which are perfectly spherical and are supplied individually packaged and gas sterilised in ethylene oxide. Spheres are available 35 mm (horse) and 25 mm (pony/Arab) sizes and are provided with instructions on how we feel they should be utilised.

Intra-uterine spheres are only supplied to a veterinary surgeon or veterinary practice for horses under their care upon a written e-mail request. One of our veterinary team will be happy to discuss medical or surgical options and alternatives available to suit your clients’ requirements.

A note to all mare owners: Your own veterinary surgeon should be your first source of advice regarding your mare’s behavioural issue(s), we are happy to advise you regarding, and/or treat your mare but this is best done via your own veterinary surgeon as a referral. If your vet feels a sphere would be useful we will happily supply one to them.


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