199 Ovarian follicle flushing as a means of retrieving oocytes in bovine ovum pickup/in vitro production
R. J. Simmons A B , D. A. R. Tutt B , W.-Y. Kwong B , G. Guven-Ates B , J. I. Baroni A B , L. N. Lim C , R. Cimpeanu D E , A. A. Castrejon-Pita F , M. Vatish C G , P. Svensson H , R. Piegsa H , U. Hagby H , K. D. Sinclair B and E. X. Georgiou C IA Paragon Veterinary Group, Dalston, Cumbria, UK
B School of Biosciences, University of Nottingham, Sutton Bonington Campus, Leicestershire, UK
C Women’s Centre, John Radcliffe Hospital, Oxford University Hospitals, Headley Way, Headington, Oxford, UK
D Mathematical Institute, University of Oxford, Oxford, UK
E Mathematics Institute, University of Warwick, Coventry, UK
F Department of Engineering Science, University of Oxford, Oxford, UK
G Nuffield Department of Women’s & Reproductive Health, University of Oxford, Women’s Centre, John Radcliffe Hospital, Oxford, UK
H Vitrolife Sweden AB, Västra Frölunda, Sweden
I Reproductive Services Unit, The Royal Women’s Hospital, Parkville, Melbourne, Australia
Reproduction, Fertility and Development 35(2) 228-228 https://doi.org/10.1071/RDv35n2Ab199
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Yield of quality oocytes is key to maximising embryo production and live births in bovine ovum pickup (OPU)/in vitro production (IVP). Although flushing follicles (with small volumes of fluid) following initial aspiration has not been found to improve oocyte recovery and development in human assisted reproduction, no equivalent data exist for cattle. Here we investigated whether the technique of follicle flushing could lead to high yields of developmentally competent oocytes in cattle and, in so doing, evaluate a novel follicle-flushing needle design. A pilot study recovered oocytes from 189 abattoir-derived ovaries over six replicates and compared two types of double-lumen needle (Vitrolife, Sweden). The first (Control) was a standard 15 g × 455 mm double lumen design, flushing parallel to the shaft of the needle, while the second (OxIVF) was of matched dimensions, but flushed perpendicular to the needle shaft at a point around 7 mm from the needle tip. Both groups used alternate flush and aspiration rates of 15 mL/minute (−70 mmHg) in follicles ≥ 7 mm in diameter. Oocyte recovery and grade were assessed. In a follow-up study, 12 Holstein heifers underwent two stimulated cycles of OPU in a crossover design. That is, six heifers were flushed with the OxIVF needle and six with the Control in Cycle 1, and then swapped between treatments in Cycle 2. Net flow rates were 15 mL/minute for both flush and aspiration in follicles ≥ 7 mm in diameter. Recovered oocytes were graded and underwent IVP as described previously (Tutt et al. 2021 Theriogenology 161, 108–119), and follicle count and embryo development to Day 8 assessed. Proportion data (both studies) were analysed by logistic regression; donor formed the random effect (follow-up study) in these mixed-linear models, and data are presented as means ± s.e.M. In the pilot study, oocyte recovery per follicle was greater (P = 0.034) proportionately for the OxIVF (0.741 ± 0.0209) than the Control (0.670 ± 0.0223) needle. The proportion Grade I of total oocytes was also greater (P < 0.001) for the OxIVF (0.273 ± 0.0271) than the Control (0.122 ± 0.0216) needle. In the follow-up OPU study, oocyte recovery was again greater (P = 0.045) for the OxIVF than the Control needle (0.891 ± 0.0298 vs 0.796 ± 0.0347). By Day 6 of culture, the proportion of morulae and blastocysts was greater (P = 0.017) for OxIVF than Control (0.872 ± 0.0438 vs 0.676 ± 0.0673); the Control needle yielded a higher (P = 0.017) proportion of developmentally retarded (>12 cells) embryos (0.324 ± 0.0673 vs 0.128 ± 0.0440). There was an indication (P = 0.075) that these differences persisted to Day 8 and led to an increased (P = 0.127) proportion of hatched blastocysts for the OxIVF needle (0.327 ± 0.0676 vs 0.231 ± 0.0697). Ovarian-follicle flushing is a recovery method that can lead to high yields of quality oocytes contributing to IVP success in stimulated cycles of OPU in cattle.
This research was supported by Innovate UK (105142); University of Oxford Challenge Seed Fund (477).
