12 Relationship between Angus oocyte quality and embryo production
D. Demetrio A , M. Oliveira A , R. Reis Silva B , D. Amorim C , C. Demetrio C and R. Santos DA RuAnn Genetics, Riverdale, CA, USA
B Federal University of Goias, EVZ, Goiania, GO, Brazil
C University of São Paulo, ESALQ, Piracicaba, SP, Brazil
D Federal University of Uberlandia, Uberlandia, MG, Brazil
Reproduction, Fertility and Development 35(2) 131-131 https://doi.org/10.1071/RDv35n2Ab12
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
The objective of this study was to evaluate the relationship between the quality of cumulus-oocyte complexes (COCs) and in vitro embryo production (IVP). In February 2022, in Riverdale, CA, USA, COCs (n = 211) from 12 Angus donors synchronised and stimulated with FSH were aspirated, pooled, and divided into grade 1 (n = 52), grade 2 (n = 59), grade 3 (n = 57), and grade 4 (n = 43), according to the oocyte classification described in appendix 2 of the fifth edition of the IETS Manual (2021), taking into consideration the appearance of the ooplasm and cumulus cells. Ovum pickups (OPUs), in vitro maturation, fertilisation, and culture (IVC) were performed as described by Demetrio et al. (2020) (Anim. Reprod. 17, e20200053). Grades 1 to 4 COCs had 53.8%, 47.5%, 21.1%, and 25.6% embryo development rates (EDRs), respectively. Grades 1 and 2 combined had higher EDRs (50.4%) than 3 and 4 (23.0%); based on that, a second study was conducted by combining the COCs into two groups: high quality (grades 1 and 2) and low quality (grades 3 and 4). Results from 1,715 pooled COCs from 107 Angus OPUs fertilised with Angus conventional semen (same collection code) and from 7 IVP cycles (48 different culture drops) performed in May and June 2022 are shown in Table 1. The embryos were classified 7 days after fertilisation, in accordance with appendix 3 of the sixth edition of the IETS Manual (2022), and divided into two groups: high-quality embryos (HQE, grade 1 expanded or hatching blastocysts) or low-quality embryos (LQE, all other viable embryos that were not HQE). A quasi-binomial model was used to analyse the proportion data to verify whether there were differences among the oocyte groups in cleavage rates, EDR-T (total embryos divided by the number of COCs in IVC), and EDR-HQE (HQE divided by the number of oocytes in IVC). LQE were discarded and HQE were transferred 7 days after expected oestrus in lactating Jersey recipients synchronised with double OvSynch. Pregnancy diagnosis was performed 33 to 44 days after expected oestrus. Higher quality COCs resulted in higher cleavage rates and EDRs. A total of 300 pregnancies resulted from 533 embryo transfers (56%). In conclusion, high pregnancy rates can be achieved when fresh, high-quality embryos are transferred to synchronised lactating recipients. However, laboratory quality control and procedures must be rigorous to ensure a high correlation between COC grades and in vitro embryo production rates. A high number of high-quality oocytes at the beginning of the process is the key factor determining high embryo production and pregnancy rates.
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This research was supported by RuAnn Genetics.
