Comparison of Two Different Schemes of Once-weekly Ovum Pick Up in Dairy Heifers

To compare two different schemes, continuous scheme (CS) and discontinuous scheme (DCS), of once-weekly ovum pick up (OPU) with ultrasound-guided follicular puncture technique, Holstein heifers were randomly divided into two groups of five. After characterization of their two normal estrous cycles, the heifers were subjected to consecutive 20 weeks of once-weekly OPU under two schemes: the CS (one week interval between continuous OPU, total 100 OPU sessions performed) and the DCS (OPU fixed to the day 3 and day 10 of each estrus). Then, the status of ovaries and artificial insemination results were observed. On oocyte yield, the total number of punctured follicles using DCS was lower than that using CS, but the mean numbers of punctured follicles and recovered oocytes per session were higher in DCS than CS group. So the total number of recovered oocytes was similar in both groups. There were also no differences in the quality of recovered oocytes, nor in the developmental ability of oocytes fertilized in vitro between groups. The heifers in the DCS group showed regular estrous cycles with stable estrous signs through the periods of before, during, and after OPU, while those in CS group showed longer estrous cycles and less estrous signs during and/or after OPU compared with before period. Furthermore, the mean number of inseminations required for obtaining pregnancy after completion of the experiments was lower in DCS than CS group. The research demonstrates that similar quantity and quality oocytes can be achieved, and the side effects on donors are lower in DCS that needs fewer OPUs than CS group, and DCS is superior to CS.