Ultrasound-guided follicle aspiration: The collection of bovine cumulus-oocyte complexes from ovaries of slaughtered or live cows

To increase the collection efficiency of bovine cumulus-oocyte-complexes (C OCs) by transvaginal aspiration, the effects of aspiration pressure and nee dle diameter on bovine follicular oocyte collection were assessed. Oocytes were aspirated from ovaries of slaughtered cows using 2 different diameter needles (18- or 21-gauge) with 4 different aspiration pressures (40, 80, 12 0 or 160 mmHg) and of live cows using 18-gauge needles with 40 or 80 mmHg, or using 21-gauge needles with 80 or 120 mmHg. The recovered oocytes were d ivided into 4 categories according to the surrounding cumulus cells and qua lity of oocytes: 1) 4 or more layers, 2) between 1 and 3 layers, 3) complet ely or partially denuded and 4) all others, including expanded cumulus cell s and degenerated oocytes. The highest oocyte recovery rates from Categorie s 1 and 2 were obtained using 18-gauge needles with 40 mmHg pressure and 21 -gauge needles with 120 mmHg pressure, respectively, from the ovaries of sl aughtered cows. When oocytes were collected from live cows, the highest rec overy rates for Categories 1 and 2 were obtained using an 18-gauge needle a nd 40 mmHg pressure, and 21-gauge needle and 80 mmHg, respectively. In addi tion, the proportion of oocytes in each category were compared between ovar ies from slaughtered and live cows. The proportion of Category 1 oocytes co llected from live cows was lower than from slaughtered cows when 18-gauge n eedles at 80 mmHg (P<0.05). The results show that the combination of aspira tion pressure and needle diameter is crucial for COC collection, and they s uggest that optimal aspiration conditions for ovaries of slaughtered cows a re not necessarily applicable to live cows. (C) 1999 by Elsevier Science In c.