8 Jersey in vitro embryo production data
D. Demetrio A , M. Oliveira A , T. Baumgartner B , C. Demetrio C and R. Santos DA Ruann Genetics, Riverdale, CA, USA
B Jer-Z-Boyz Ranch, Pixley, CA, USA
C Universidade de São Paulo, Piracicaba, SP, Brazil
D Universidade Federal de Uberlândia, Uberlândia, MG, Brazil
Reproduction, Fertility and Development 34(2) 237-238 https://doi.org/10.1071/RDv34n2Ab8
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
The combination of low oocyte recovery, young age of donors, and milk production status can make in vitro embryo production (IVP) of dairy cattle challenging. The objective of this study was to evaluate oocyte and embryo production from Jersey heifers and lactating donors from Jer-Z-Boyz Ranch, located in Pixley, California (4500 cows in milk). Ovum pick-up (OPU) and IVP data were collected between December 2019 and April 2021. Jersey heifers (11 to 13 months) or lactating cows were used as oocyte donors and were selected by genetic merit not by the quantity of oocytes produced. Most donors were 35 to 80 days pregnant at the time of OPU (75%). All animals were stimulated with 1 or 5 (10- to 14-h interval) IM injections of follicle stimulating hormone (FSH, Folltropin®, Vetoquinol, USA; 175 IU for cows or 105 IU for heifers), 36 h after synchronisation with gonadorelin (GnRH, Fertagyl®, Merck Animal Health, USA, 129 μg, IM). OPU was performed 46 to 52 h after the single injection FSH protocol or 24 to 30 h after the multiple injection protocol. OPU, oocyte classification, IVM, IVF, and in vitro culture (IVC) were performed at the RuAnn Genetics laboratory as described by Demetrio et al. (2020 Anim. Reprod. 17, e20200053). Grade 1 to 4 oocytes went into IVM and grades 1 and 2 were considered high quality. Oocytes that cracked or had retracted ooplasm after IVF were not placed into culture. The embryo development rates were defined as the number of Day 7 embryos (morulas to hatched blastocysts) that were transferred fresh or cryopreserved divided by the number of oocytes in IVC (EDR-T), or by the number of high-quality oocytes (EDR-1,2). Poisson-normal (count data) and logistic-normal (proportion data) models were fitted to the data. Donor oocyte recovery group (≤15 oocytes vs. >15 oocytes), donor status (heifer vs. cow), and donor and sire (random effect) were included in the models to analyse the proportion of high-quality oocytes and EDRs. Results are shown in Table 1. A higher percentage of heifers produced fewer than 15 oocytes compared with lactating donors (85.7% vs. 48.7%). There was a 16% reduction in the number of oocytes from IVM to IVC. Oocyte recovery and embryo production were highly donor and sire dependent (P < 0.05). Donors that had more oocytes recovered by OPU produced more embryos, but there was no difference in the proportion of good oocytes and EDRs. Donor selection would be a good strategy to produce more embryos per OPU as long as we do not mind not producing offspring from the highest-genetic-merit donors that are young or do not have many oocytes.
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