Oral Presentation ESA-SRB 2023 in conjunction with ENSA

Multiplication of bovine embryos via blastomere separation techniques (#29)

Danielle Azoulay 1 , Nicholas I. Cameron 2 , Wilhelmus T.L. te Brake 2 , Michael B. Morris 1 , Margot L. Day 1
  1. School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
  2. Nbryo Pty Ltd, Brisbane, QLD, Australia

As the global population grows, the demand for dairy (bovine) and beef products rises. Efficient production of large numbers of high-quality livestock can help alleviate protein shortages. Embryo twinning offers a significant opportunity to amplify numbers of transferable embryos. Twinning can be artificially induced by separating blastomeres of cleavage-stage embryos and culturing them to create multiple blastocysts. Previously, blastocysts have been obtained from individual blastomeres from 2-cell, 4-cell and 8-cell stage embryos in bovine and other species (1,2,3,4,5). However, the maximum number of embryos produced from a single embryo was four (2,4).

This work aims to enhance bovine embryo twinning for production of viable calves. Blastomeres from 2-, 8-, 16-, or 32-cell embryos were separated and cultured to the blastocyst stage, individually, in pairs or quads. Blastomeres were either separated once (N=1 separation) or serially separated at the 2-cell stage, and then at each subsequent cleavage for three cleavages (N=4 separations). There was no difference in blastocyst formation from serial N=4 separations, from the 2-cell stage (19.5%) compared to N=1 separation at the 16-cell stage (17.6%). Pairs of blastomeres separated at 8-, 16-, and 32-cell stages developed to the blastocyst stage better than individual blastomeres, regardless of cell stage. Additionally, culture of quads of blastomeres, separated at the 32-cell stage, resulted in greater blastocyst development (61.4%) than pairs separated at the 8-cell (26.6%), 16-cell (47.2%) and 32-cell (29.1%) stages.

Preliminary embryo transfer studies, with blastocysts derived from either pairs or quads, resulted in 29.6% (n=27) and 36.4% (n=11) pregnancies and birth of 6 and 2 calves, respectively. In conclusion, blastomere separation techniques present an appealing approach for large scale production of embryos for improvement of genetic gains from high quality donors and sires.

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