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Vertebrate reproductive science and technology
RESEARCH ARTICLE

Conditions to optimise the developmental competence of immature equine oocytes*

Elizabeth S. Metcalf https://orcid.org/0000-0003-0601-799X A B G , Keith R. Masterson B , David Battaglia B , Jeremy G. Thompson C , Robert Foss D , Richard Beck E , Nancy L. Cook https://orcid.org/0000-0001-8952-5396 F and Thomas O’Leary B
+ Author Affiliations
- Author Affiliations

A Honahlee PC, 14005 SW Tooze Road, Sherwood, OR 97140, USA.

B Andrology Division, Department of Obstetrics and Gynecology, Oregon Health and Science University School of Medicine, 3303 S. Bond Avenue, Portland, OR 97239, USA.

C School of Medicine, The University of Adelaide, Medical School, South Adelaide, SA 5005, Australia.

D Equine Medical Services, 5851 E Deer Park Road, Columbia, MO 65201, USA.

E In Foal, Inc., 39185 Diamond Valley Road, Hemet, CA 92543, USA.

F Advanced Equine Reproduction, 1145 Arroyo Mesa, Solvang, CA 93463, USA.

G Corresponding author. Email: honahlee@imagina.com

Reproduction, Fertility and Development 32(11) 1012-1021 https://doi.org/10.1071/RD19249
Submitted: 15 July 2019  Accepted: 11 June 2020   Published: 9 July 2020

Abstract

Optimising the developmental potential of immature equine oocytes and in vitro-produced (IVP) embryos was explored through modifications of established media and holding temperature. In Experiment 1, delaying spontaneous resumption of meiosis through the process of simulated physiological oocyte maturation with the addition of the adenylate cyclase activator forskolin (50 µM) and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (100 µM) to overnight holding medium before maturation improved blastocyst production (P < 0.05). In Experiment 2, the blastocyst production rate was increased significantly when cumulin (100 ng mL−1) was added to the overnight holding or culture media (P < 0.05). In Experiment 3, immature oocytes held overnight at 16°C before maturation had improved developmental competence than those held at 20°C and 5°C (P < 0.05). There was no difference between maturation rates, but blastocyst formation per cleaved oocyte was significantly greater in oocytes held overnight at 16°C than at 20°C or 5°C. Furthermore, blastocyst formation per recovered oocyte and per fertilised oocyte was greater when oocytes were held before maturation at 16°C than at 5°C (P < 0.05). In Experiment 4, the addition of sodium ascorbate (AC; 50 µg mL−1) to the maturation and/or culture media of oocytes and IVP embryos did not improve blastocyst production, but did appear to lower cleavage rates compared with oocytes and embryos cultured without AC.

Graphical Abstract Image

Additional keywords: blastocyst, cell culture, intracytoplasmic sperm injection, IVF, IVM.


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