Effects of follicular aspiration system on the results of transvaginal ultrasound-guided ovum pick-up in cattle

Recently, the transvaginal ultrasound-guided ovum pick-up (OPU) has been developed to collect oocytes from live cows for in vitro production of bovine embryos. Although various OPU systems have been developed and used, the systems can be improved in terms of ways; the recovery rate of cumulus-oocyte complex (COC), ease of handling and cost. This study was carried out to develop an OPU system in cattle, where twisting and type of aspiration needles, and tubing system were emphasized. First, the effect of twisting the needle during follicular aspiration on the recovery rate of COCs was investigated using ovaries from slaughter-house, by a long single-lumen needle. The results revealed that needle twisting increased the recovery rate of oocyte with cumulus cells. Secondly, the effects of vacuum pressure on the COC recovery rate were examined using four OPU systems assembled with different type of needles (long or short single-lumen, or long double-lumen) and tubings with or without junctions. As the results, the most suitable vacuum pressure (flow rate) observed for follicle aspiration was 50 or 75mmHg(7.5-15.0ml/min) in all OPU systems. It was thus, observed that tubing with junctions reduces the COC recovery rate, double-lumen needle was suitable and efficient for follicle aspiration. At the end, the OPU from live cows was performed using follicle aspiration system with long and short single-lumen needles and a long double-lumen needle attached to two kinds of hand-made probe-carrier. The system with a long single-lumen needle significantly decreased the COC recovery rate and the proportion of normal COCs with several cumulus layers.