Use of frozen-thawed semen in equine artificial insemination programmes

Abstract

The use of equine frozen semen has variable results. Pregnancy rates per cycle may be between 10 to 70%. Although an inseminating dose of 280 a 320 millones progressive motile sperm (PMS) has been recommended, under experimental conditions it is posible to obtain acceptable results with doses of 50 to 100 millones PMS. Deep intrauterine insemination is prefered when using frozen thawed semen, which consists in depositing the dose at the tip of the horn, ipsiltateral to ovulation. Young mares usually have better uterine condition and that increase their chance of become pregnant. It is important to make a correct follicular monitoring, in order to determine the right time to induce ovulation. Ovulation may be induced with Human Chorionic Gonadotrophin (hCG) or deslorelin. It posible to perform a fixed time insemination or to choose an ultrasound follicular following protocol, inseminating within 6 h of ovulation. This option offers the best prenancy rates. Our laboratory manages a protocol which includes ultrasound monitoring every 6 hours, beginning 24 hous after induction of ovulation; this protocol had a first insemination pregnancy rate of 73%. If we consider that one of the main disadvantages of frozen-thawed semen is decreased fertility, these results are encouraging, since they are similar to those obtained with fresh or cooled semen, so it may represent an advantage when having stored semen of stallions that are dead, or have been sold or even castrated.

Keywords

• equine
• frozen semen
• insemination
• inseminating dose