Mithun (Bos frontalis), a unique free - range bovine species available in the North Eastern hill region of India. Recent statistics indicates that the mithun population is decreasing gradually due to lack of suitable breeding bulls, increase in intensive inbreeding practices,etc. in this region. Greater efforts are required from all quarters to preserve the mithun population. Since mithuns are semi wild animal and not fully domesticated, natural breeding is practiced in this species with accompanied limitations like cost and disease transmission. Thus, use of artificial insemination and frozen semen technology for improvement of its pedigree is utmost essential. One cause of decline of semen quality in preservation is due to the action of the reactive oxygen species generated by the cellular components of semen. The effects of lipid peroxidation include irreversible loss of motility, damage to the sperm DNA and fertility. So preservation of mithun semen with anti-oxidants such as catalase (CAT), reduced glutathione, cysteine hydrochloride,trehalose, bovine serum albumin and superoxide dismutase (SOD) are essential to offset lipid peroxidation and enhance the fertility.