EFFECTS OF ONCE-WEEKLY VERSUS TWICE-WEEKLY TRANSVAGINAL FOLLICULAR ASPIRATION ON BOVINE OOCYTE RECOVERY AND EMBRYO DEVELOPMENT

Ultrasound-guided transvaginal follicular aspiration combined with in vitro maturation/in vitro fertilization (IVM/IVF) and culture was used to obtain bovine preimplantation stage embryos. Evaluated were the ef fects of aspiration frequency on oocyte recovery and embryo developmen t following IVM/IVF. In Experiment 1, transvaginal follicular aspirati on was performed once (n=5) or twice (n=5) weekly in multiparous Angus cows with the aid of a transvaginal sector transducer (5-MHz). In Exp eriment 2, aspiration was performed on Angus cows once weekly (n=6), t wice weekly (n=4), or twice weekly after treatment with FSK (15 mg; n= 4) Follicles (>2 mm) were punctured using a 55-cm needle (17-g), and o ocytes were aspirated through the needle and silastic tubing (2 m) by vacuum suction (75 mmHg). The oocytes were examined for morphology and were in vitro matured and fertilized. Following IVF, all ova were co- cultured in vitro for 7 d on Buffalo Rat liver cells. Oocyte recovery rates per aspiration session in Experiment 1 were not different betwee n groups aspirated once or twice weekly (6.8+/-2.0 vs 6.3+/-1.1 oocyte s/session; ($) over bar X+/-SEM) or in Experiment 2 between groups asp irated once, twice, or twice plus FSH treatment (7.7+/-1.8 vs 9.5+/-1. 1 vs 6.2+/-1.1; P>0.10). In vitro development to the blastocyst stage was not different between the once, twice or twice-weekly aspiration p lus FSH treatments or control oocytes obtained from cows at slaughter (23.1 vs 26.1 vs 18.0 vs 27.9%; P>0.10) Oocytes from the twice-weekly and twice-weekly plus FSH aspiration groups generated a higher percent age of Grade-1 quality embryos than the once-weekly group (P<0.05) In commercial bovine oocyte aspiration, more transferable embryos can be generated from twice-weekly aspirations than from once-weekly aspirati on.