The aims of this study was to see the effect of breed, parity and scheme of collection on the quality and quantity of OPU derived oocytes and effect of transvaginal ultrasound guided follicular aspiration on subsequent fertility of donor cows. A total of 28 animals (11 Boran and 11 Boran Holstein-Friesian cross for once per week collection, and 7 Boran and 7 Boran Holstein-Friesian cross for twice per week collection) were used in this experiment. A total of 22 animals were evaluated for the effect of the OPU procedure on subsequent reproductive function. In 150 Ovum Pick up sessions, irrespective of collection scheme, breed and parity, 1124 follicle (554 in Boran and 570 in HF crosses) were punctured with a recovery rate of 51.1% in Boran and 48.6% in the crosses. Relatively more follicles were aspirated in crosses compared to Borans although the difference in oocyte recovery rate and quality were not statistically significant. Overall recovery rate was 57.7% in heifers and 42% in cows. Frequency of aspiration significantly influenced (P<0.05) oocyte recovery rate with more follicles aspirated in Once per week per session compared to twice per week per session but there was no difference in the mean number of recovered oocytes. A significantly higher number of follicles were aspirated (P<0.05) and good quality oocytes were greater in heifers than cows. Different COCs quality grades were recovered from breed, parity and frequency of collection category. Overall from a total of 574 collected COCs, about 326 (57%) of the recovered COCs were of the quality grades I and II, whereas 248 (43%) were with quality grades III and IV. All 22 animals showed estrus on average after 19 days of the last OPU procedure though a relatively weaker intensity of estrus signs, irregularity of the cycle and minor ovarian morphological change were noted. Response rate to a single PGF2α treatment on 18 animals was 72% (13/18). Subsequent insemination of those in estrus resulted in 53.8% (7/13) first service conception rate. In conclusion, parity, and to some extent frequency of collection had a significant effect on the quality and quantity of oocyte but not breed. Animals at post OPU were able to continue cycling and become pregnant.
 Aller, J.F., Mucci, N.C., Kaiser, G.G., Callejas, S.S. and Alberio, R.H. (2012): Effect of repeated eCG treatments and ovum pick-up on ovarian response and oocyte recovery during early pregnancy in suckling beef cows. Anim Reprod Sci. 133: 10-15
 Apimeteetumrong, M., Liengchareon, N., Thuangsanthi, A., Yiengvisavakul, V., Thijae, K. and Sumretprasong, J. (2009). Embryo production of Kao Lumpoon cattle using ovum pick-up and In vitro fertilization techniques. The 10th KKU Veterinary Annual Conference 2009. p 168-172
 Bols PEJ, Van Soom A, Ysebaert MT, Vandenheede JMM, de Kruif A. (1996): Effects of aspiration vacuum and needle diameter on cumulus oocyte complex morphology and developmental capacity of bovine oocytes. Theriogenology 45: 1001-1014
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