Evaluation of transvaginal ultrasound-guided follicle puncture to collect oocytes and follicular fluids at consecutive times relative to the preovulatory LH surge in eCG/PG-treated cows.

Holstein-Friesian cows (n=56) were synchronized with Syncro-Mate B, and those cows (n=47) developing a normal progesterone pattern were further treated im with 3,000 I.U. eCG at Day 10 and 22.5 mg PGF2alpha 48 h later. Blood samples were collected every hour from 30 until 49 h after PG administration. Cows (n=17, 36.2%) with fewer than 8 follicles larger than 8 mm in diameter at 28 to 30 h after PG treatment and animals without an LH peak (n=7, 23%) were excluded from the study. Transvaginal ultrasound-guided puncture of the follicles was carried out two times per cow, at 30 h after PG injection (4 to 5 follicles) and again at 1 to 5 (n=6), 12 (n=8) or 22 h (n=9) after the LH peak. No differences in the concentrations of progesterone and LH were observed among the 3 groups. An average of 18 follicles per cow was punctured (total of 415 punctures, n=23); 116 cumulus-oocyte-complexes and 370 follicular fluid samples were obtained producing average recovery rates of 28.0% and 89.2%. The number of cumulus-oocyte-complexes varied between puncture times; shortly before ovulation, at 22 h after the LH peak, the recovery rate was significantly 5 times higher than immediately after the LH peak. Overall, in 75 punctures the cumulus-oocyte-complex was accompanied by a pure follicular fluid sample (3.3 per cow). In conclusion, the transvaginal ultrasound-guided puncture of preovulatory-size follicles can be used to collect follicular fluids to study changes in the microenvironment of maturing oocytes upon superovulation. However, further research is required in order to obtain an equivalent number of accompanying cumulus-oocyte-complexes.