Transvaginal collection and ultrastructure of llama (Lama glama) oocytes

Ultrasound-guided transvaginal follicle aspiration has been described as a noninvasive and repeatable procedure for oocyte collection in several speci es, but its use has not been described for any of the members of the family , Camelidae. A study was designed to determine the feasibility of an ultras ound-guided transvaginal approach for oocyte collection in llamas. Fifteen non-pregnant, adult female llamas (10 non-stimulated and 5 superstimulated) were examined by transrectal ultrasonography with a 7.5-MHz linear-array t ransducer to determine the number and diameter of follicles available for a spiration. After caudal epidural anesthesia was induced, the 7.5-MHz linear -array transducer was fastened to a long rigid handle and inserted intravag inally. The free hand was placed into the rectum to manipulate the ovaries, one at a time, in position against the vaginal wall over the face of the t ransducer. A 20-gauge, 55-cm-long, single-lumen needle was advanced through the vaginal formix and into follicles greater than or equal to 3mm in diam eter. Follicular contents were aspirated using a regulated vacuum pump (flo w rate = 33 mL/min; approximately 150 mm Hg) into a tube containing 3 mL of phosphate buffered saline and 0.2% BSA. Fluid was filtered (75 mum mesh), and oocytes were located and morphologically evaluated using a stereomicros cope. Overall, 134 follicles were aspirated, and 76 oocytes were collected (collection rate = 57%). Thirty-two oocytes (42%) were surrounded by multip le layers of compacted granulosa cells and had homogenous dark ooplasm; 13 oocytes (17%) were surrounded by the corona radiata layer only and had heav ily granulated ooplasm; 9 oocytes (12%) were denuded and had homogenous dar k ooplasm; and 22 oocytes (29%) were denuded and displayed signs of ooplasm degeneration. The ultrastructure of llama oocytes was similar to that of c attle except for conspicuous accumulation of large lipid droplets in the cy toplasm. Twenty-four hours after follicle aspiration, the ovaries were exam ined by transrectal ultrasonography and intrafollicular hematomas were dete cted in 3 llamas (9 of 48 follicles aspirated). Results demonstrate the pot ential utility of a transvaginal ultrasound-guided technique for oocyte col lection and in vitro embryo production in llamas. Oocytes of llamas bear an ultrustructural resemblance to those of cattle, but are distinguished by a predominance of cytoplasmic lipid. (C) 2000 by Elsevier Science Inc.