Horse embryo diameter is influenced by the embryonic age but not by the type of semen used to inseminate donor mares.
Abstract: The diameter of embryos recovered from mares on Day 8 after ovulation varies greatly, from as little as 130 μm to as much as 2500 μm. Several factors have been proposed to affect embryo size at recovery, one of which is the type of semen (frozen vs fresh or cooled-transported) used to inseminate the mare. In addition, it has been shown that smaller embryos (<300 μm) recovered on Day 8 are less likely than larger embryos to result in successful pregnancy after transfer. However, whether the actual age of the embryo (interval from fertilization to flushing) in relation to its size also influences the post-transfer viability is unclear. The aims of this study were: a) To determine the effect of semen type (frozen-thawed vs cooled-transported) on embryo diameter after pre-ovulatory insemination; and b) To establish the relationship between embryonic age, embryo size and likelihood of pregnancy and pregnancy loss following transfer. A total of 179 embryos were recovered from mares inseminated with: frozen semen post-ovulation 8 days previously (G1; n = 35); cooled-transported semen pre-ovulation 8.5 days previously (G2; n = 95); frozen semen pre-ovulation 8.5 days previously (G3; n = 30); and frozen semen post-ovulation 9 days previously (G4; n = 19). The effect of embryonic age, type of semen, donor mare and its age, number of ovulations and embryos per flush on embryo diameter was tested using a general linear model of variance. In addition, the proportions and survivals of small embryos (<300 μm) in each group were compared with those of respective larger embryos by Fisher's exact test. Embryonic age (P < 0.001) and age of the donor mare (P = 0.07), but no other factor, influenced embryo diameter. The proportion of small embryos was 42.9, 10.5, 10.0 and 10.5% for Groups 1, 2, 3 and 4, respectively. The pregnancy status of recipient mares 35 days post-transfer for small embryos from Group 1 (12/15; 80.0%) was not different (P > 0.1) from that of recipients of small embryos from Groups 2 to 4 combined (8/15; 53.3%).
Copyright © 2018 Elsevier Inc. All rights reserved.
Publication Date: 2018-04-27 PubMed ID: 29734126DOI: 10.1016/j.theriogenology.2018.04.023Google Scholar: Lookup
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- Journal Article
Summary
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The research investigates whether the type of semen (frozen or fresh) used to impregnate mares has an effect on the diameter of the recovered embryos, along with an analysis of how embryonic age and size influences the likelihood of successful pregnancy. The study concluded that embryonic age and the age of the donor mare have a significant effect on embryo diameter, but the type of semen used for insemination doesn’t.
Study objectives and design
- The study aimed to understand the impact of the type of semen (frozen-thawed vs. cooled-transported) on the size of horse embryos. Moreover, it looked to establish the connection between embryonic age, embryo size, and subsequent pregnancy outcomes.
- A total of 179 embryos were retrieved from mares that had been inseminated with various combinations of semen type and insemination timing (Pre or Post ovulation).
- A general linear model of variance was utilized to understand the influence of various factors (embryonic age, semen type, donor mare age, number of ovulations, and embryos per flush) on the embryo size.
- The proportions and viability of small embryos (less than 300 μm) across all groups were compared with respective larger embryos using Fisher’s exact test.
Results and interpretation
- The study found that the age of the embryo (P < 0.001) and the age of the donor mare (P = 0.07), but no other factor, had a noticeable impact on the diameter of the embryo. This indicates that as the embryo or the donor mare is older, the embryos tend to be larger in diameter.
- The proportion of small embryos varied across groups, with Group 1 (inseminated with frozen semen post-ovulation 8 days previously) having a significantly higher proportion (42.9%) compared to the other groups.
- The study, however, found no significant difference in pregnancy status among recipient mares receiving small embryos from different groups 35 days post-transfer. The results suggest that no matter the type of semen used, the likelihood of a successful pregnancy doesn’t show a significant difference.
Conclusions
- Therefore, the study concluded that the type of semen used, whether it was cooled-transported or frozen-thawed, doesn’t influence the diameter of the embryos. What matters more are the embryonic age and the age of the donor mare.
Cite This Article
APA
Cuervo-Arango J, Claes AN, Stout TAE.
(2018).
Horse embryo diameter is influenced by the embryonic age but not by the type of semen used to inseminate donor mares.
Theriogenology, 115, 90-93.
https://doi.org/10.1016/j.theriogenology.2018.04.023 Publication
Researcher Affiliations
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, The Netherlands. Electronic address: j.cuervo-arangolecina@uu.nl.
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
- Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
MeSH Terms
- Abortion, Veterinary / epidemiology
- Animals
- Embryo Transfer / veterinary
- Embryo, Mammalian / anatomy & histology
- Female
- Gestational Age
- Horses / embryology
- Insemination, Artificial / methods
- Insemination, Artificial / veterinary
- Ovulation
- Pregnancy
- Pregnancy Outcome / veterinary
- Semen / physiology
- Semen Preservation / methods
- Semen Preservation / veterinary
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