Effect of the inseminate and the site of insemination on the uterus and pregnancy rates of mares

In this review, effects of the composition of the inseminate on uterine response and pregnancy rates in mares are discussed. The inseminate can differ for volume, sperm concentration, total sperm numbers, presence, absence, or proportion of seminal plasma, and extender composition. Semen can be used as fresh, cooled, or frozen. The site of semen deposition also plays a role; semen is deposited either into the uterine body (standard artificial insemination (AI)) or into the tip of the uterine horn ipsilateral to the preovulatory follicle (deep AI) using the hysterocopical or transrectally guided techniques. In addition to pregnancy rates, some uterine responses to the inseminate are considered including myometrial contractions, transport and elimination of sperm, and uterine inflammation, which is reflected as numbers of polymorphonuclear leukocytes, enzyme levels, and presence of intrauterine fluid. Reproductively normal and abnormal mares are compared.