In female horses, oestrus behaviour is often associated with a moody temperament and undesired behaviour with regard to their use in equestrian activities (Pryor & Tibary, 2005). The behaviour of mares is therefore often detrimental to their performance Stout & Colenbrander, 2004). Trainers, riders and persons handling mares frequently complain about such problems and demand for methods to suppress gonadal function with the aim to reduce oestrus