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Ovarian follicular flushing as a means of increasing oocyte yield and in vitro embryo production in cattle

Robert Simmons , Desmond Tutt, Wing Yee Kwong, Jonas Baroni, Lim Lee, Radu Cimpeanu, Alfonso Castrejon-pita, Manu Vatish, Par Svensson, Ralf Piegsa, U Hagby, Kevin Sinclair , Ektoras Georgiou

Abstract

Context: The number of developmentally competent cumulus-oocyte complexes (COCs) retrieved during Ovum Pick-Up (OPU) determines success in both bovine and human assisted reproduction. Follicular flushing for COC retrieval is practiced widely in humans but not in cattle. Aims: To determine the benefits of follicular flushing in cattle and assess the merits of a novel 16G double-lumen needle (‘OxIVF’) that flushes laterally to the needle shaft. Methods and key results: Experiment 1 flushed 655 antral follicles (≥7 mm) from 255 abattoir-derived cattle ovaries. COC recovery was greater (P = 0.034) for the OxIVF vs Standard needle (mean ± SE; 74.1 ± 2.10% vs 67.0 ± 2.23%); yield of Grade 1 COCs was also greater (20.1 ± 1.97% vs 8.2±1.38%; P < 0.001). In Expt. 2, twelve Holstein heifers underwent two cycles of OPU in a cross-over design comparing both needle types. Recovery of COCs was greater (P = 0.045) for the OxIVF vs Standard needle (89.1±2.98% vs 79.6±3.47%). Day 6 embryo yield was also greater (P = 0.017) for the OxIVF vs Standard needle (87.2±4.38% vs 67.6±6.73%). In Expt. 3, eleven Holstein heifers underwent two cycles of OPU using the OxIVF needle in a cross-over design: flushing (≥7 mm follicles) vs a ’Hybrid’ approach of flushing (≥7 mm follicles) and aspiration (5-7 mm follicles); followed by two cycles of standard follicle aspiration (> 5 mm follicles). Recovery of COCs was greater (P = 0.033) for ‘Flush’ vs ’Aspirate’ groups (82.1±5.06% vs 66.2±3.48%). However, number of Day 8 blastocysts for the ‘Hybrid’ vs ‘Flush’ approach (9.2±1.39 vs 6.5±1.05 per cycle) did not reach statistical significance. Implications: Follicle flushing using the OxIVF needle, embracing the ‘Hybrid’ approach, has the potential to increase oocyte retrieval and blastocyst number per donor cycle but requires further validation.

RD24125  Accepted 02 November 2024

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