308 PREGNANCY RATE AND EMBRYO PRODUCTION AFTER INSEMINATION OF MARES WITH SEXED SORTED SEMEN

Abstract

In the equine industry the selection of the desired sex of the offspring can be used as a tool in the improvement of a genetic program with the same advantages as cited in other species. Nevertheless, another advantage can be realized if we consider that there are some sport breeds in which females are better performers than males. As an example in polo ponies nine out of ten ponies are females and most male newborns become an undesired product because of their very low commercial value. To date it has been reported that the use of a low dose of sexed sorted semen (5 × 10⁶) resulting in pregnancy rates of 40% after hysteroscopic insemination and 50% using a deep intrauterine insemination pipette with a dose of 25 × 10⁶ non-sexed semen (Lindsey AC et al. 2001 Anim. Reprod. Sci. 68, 279–89). Considering that the hysteroscopic procedure is a time-consuming technique that requires well-trained people and expensive equipment, the aim of this study was to evaluate: (a) if the pregnancy rate obtained after insemination of mares with a low dose of fresh sexed sorted semen using the intrauterine pipette could achieve results similar to those of the hysteroscopic procedure, and (b) the possibility of embryo production and pregnancy rates after transferring those embryos. Twenty-four mares with a dominant follicle more than 35 mm in diameter were injected with 2500 UI of human corionic gonadotrophin (hCG) (Endocorion^® Elea, Buenos Aires, Argentina) and inseminated between 30 and 36 h after hCG. A total of 40 × 10⁶ sexed spermatozoa (45–55% of them were progressively motile) were deposited deeply in the ipsilateral horn to the preovulatory follicle using the deep intrauterine insemination pipette (Minitube^®, Verona, WI, USA). Ten of the 24 (40%) were inseminated with a second dose because they didn't ovulate 6 h after the first AI. The semen was provided by our commercial laboratory following the XY, Inc. (Fort Collins, CO, USA) protocol for sexing equine semen. In a subsequent study, 18 donors were inseminated following similar criteria and flushed 7.5 days after ovulation using 3 liters of a flushing medium with bovine serum (1%) and antibiotics. After the embryos were washed through 10 drops of holding medium, a single embryo was transferred into the uterine body of each of 11 recipients which ovulated between one day before to three days after the donor mare. Six days after ET, the diagnosis of pregnancy was carried out by transrectal ultrasonography (ALOKA 500 Scanner^®, Aloka Technology, Wallingford, CT, USA) and confirmed by a second scanning 25 days later. Results are shown in Table 1. According to these results, the insemination with a low number of fresh sexed sorted semen using the large intrauterine pipette had results similar to those obtained with the hysteroscopic procedure. Although we performed a low number of flushings, results showed no difference in embryo production and pregnancy rates compared with data from when non-sexed semen was used to inseminate the donors.

Table 1.
Artificial insemination and embryo transfer results with sexed semen

Current Equine Embryo Transfer Techniques D. Vanderwall, International Veterinary Information Service, Ithaca, NY, 2000.