Results of ultrasound-guided transvaginal collection of oocytes (TVA-OPU) from mares to be fertilized by intracytoplasmic sperm injection (ICSI).

The aim of this study was to present the results of transvaginal ultrasound-guided collection of oocytes (TVA-OPU) from 21 mares to be fertilized in vitro by the ICSI method. One week before the planned OPU, the mares underwent a gynecological examination with particular emphasis on the functional status of the ovaries. The recommendation for the procedure was the presence of at least 12 ovarian follicles with a diameter of at least 4 mm on both ovaries. The selected mares were given PGF2α in a luteolytic dose 3 days before the planned OPU, so that the mares were in the early proestrus stage during the procedure and did not have a corpus luteum on the ovary. If PGF2α administration was believed to increase the risk of estrus on the day of the OPU procedure, the hormone was not administered. Immediately prior to OPU, the mares were premedicated with detomidine and butorphanol. During the procedure, symptoms of anxiety or pain were controlled using the bolus agents listed above, plus flunixin as needed. A mixture of hyascin butylbromide and sodium metamizole was also used in order to eliminate an excessive tension of the rectum. After each treatment, the mares were administered procaine penicillin, benzathine penicillin, and streptomycin. All mares underwent the OPU treatment without complications. During 24 OPU procedures (3 mares underwent the procedure twice), a total of 239 oocytes (an average of 10 oocytes from 1 mare) were obtained, 137 of which were qualified for the ICSI procedure (57% of the total). After fertilization, embryonic division occurred in 95 (70% of the oocytes qualified for ICSI). Ultimately, 23 embryos were grown and preserved in liquid nitrogen (which resulted in an average of 1 embryo per 1 OPU treatment in mares) and accounted for 17% of oocytes qualified for the treatment. According to the authors' best knowledge, it was the first project of this type in our country.