Transvaginal Follicle Aspiration in Mares: A Description of Different Techniques and Comparison of Results Across Different <scp>OPU</scp> Clinics

This retrospective clinical study describes different techniques for transvaginal follicle aspiration in mares and compares results from 5 different commercial ovum pick-up (OPU) clinics in which the same operator aspirated mares using different systems and equipment: Clinic 1 (n = 42 mares, two-operator OPU technique, double-lumen-echogenic-tip needle, and manual syringe-assisted flushing of follicles), Clinic 2 (n = 28 mares, single-operator-OPU-technique, double-lumen-echogenic-tip needle, infusion pump controlled by foot-pedal for follicle flushing), Clinic 3 (n = 18 mares, single-operator-OPU-technique, double-lumen-echogenic-tip needle, and manual syringe-assisted flushing of follicles), Clinic 4 (n = 24 mares, single-operator-OPU-technique, double-lumen-non-echogenic-tip needle, and manual syringe-assisted flushing of follicles), and Clinic 5 (n = 9 mares, aspirated as in Clinic 1). The ease of performing OPU (visibility of needle tip and difficulty to hold ovary, probe, and needle) and the mean number of recovered oocytes were compared between clinics. The mean number of recovered oocytes per mare and oocytes per follicle for clinics 1-5 were 11.9 ± 4.6 and 64%, 13.5 ± 6.5 and 53%, 12.3 ± 4.2 and 54%, 9.5 ± 3.3 and 51%, and 19.9 ± 8.2 and 64%, respectively. The combined recovered oocyte per aspirated follicle was 10% higher in clinics with a 2-operator technique (clinic 1 and 5, 63.63%) than in clinics with the single-operator technique (clinics 2-4, 53.32%). The mean number of recovered oocytes was numerically greater in the clinics using the echogenic needle tip (11.9, 13.5, 12.3, and 19.9 oocytes per mare, for clinics 1, 2, 3, and 5, respectively) than in the clinic using the non-echogenic needle tip; (9.5 oocytes per mare for clinic 4). The use of a plastic syringe or an infusion pump to flush follicles did not appear to affect the number of recovered oocytes or oocyte recovery rate (clinic 2 vs. 3). The left arm of the single operator (holding OPU probe and needle) experienced fatigue more frequently when mares were aspirated singly, than when the needle was managed by a second operator. In conclusion, the oocyte per follicle recovery was 10% lower in clinics using a single-operator-OPU-technique compared with clinics using a two-operator-technique.