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Acta veterinaria Scandinavica1996; 37(3); 343-350; doi: 10.1186/BF03548100

Recovery rate and quality of embryos from mares inseminated at the first post-partum oestrus.

Abstract: The pregnancy rate is lower in mares inseminated at the first post-partum (p.p.) oestrus (40-50%) compared with pregnancy rates in subsequent oestrous cycles (55-65%). The causes of the lowered pregnancy rate are not fully understood. The aim of the present study was to examine if embryonic defects could be one of the reasons for lowered pregnancy rate. A total of 23 p.p. and 14 non-lactating control mares were flushed 7 days after detection of ovulation. Embryo recovery rate was 48% and 71% in p.p. and control mares, respectively (p = 0.16). Embryos were photographed, measured, graded and stained with fluorescein diacetate to assess their viability. Thereafter embryos were bisected and stained with Hoechst 33342 to count the cell nuclei. Embryos in both groups were equally viable and the cell numbers were not significantly different. According to morphological evaluation all embryos were classified as excellent or good. Embryos aged 7.3 to 7.6 days (+/-0.25 days) were smaller in the p.p. group than in the control group (p < 0.05). Forty-seven (9/19) and 8% (1/13) of the uterine swabs, taken before the first insemination, yielded bacteria and neutrophils in p.p. and control mares, respectively. The amount of neutrophils and/or bacteria had no statistically significant effect on embryo recovery rate (p > 0.10). Recovery of embryos was not related to histological findings in uterine biopsies taken after embryo recovery. Embryo recovery rate in p.p. mares (48%) was similar to previously reported foal heat pregnancy rates (40-50%). Hence, early embryonic death in utero would not be the most likely reason for lowered pregnancy rate in mares inseminated at the first p.p. oestrus. Sperm transport and oviductal conditions by the time of the first p.p. oestrus would need to be studied to clarify the role of fertilisation failure as the cause of lower pregnancy rate in mares inseminated at foal heat. Dräktighetsprocenten är lägre hos ston inseminerade i den första post-partum brunsten. Embryourspolning användes för att utreda om defekter i embryon var en av orsakerna till lägre dräktighetsprocent. Embryon från 23 post-partum och 14 icke-lakterande kontrolllston urspolades 7 dagar efter en uppskattad ovulation. Frekvensen funna embryon var 11/23 (48%) och 10/14 (71%) hos post-partum respektive kontrollston. Skillnaden var inte statistiskt signifikant (p = 0,16). Embryona färgades med fluorescein diacetat för att bedömma deras vitalitet, och med Hoechst 33342 för att räkna antalet cellkärnor. Embryona i de båda grupperna uppvisade samma vitalitet och deras cellantal var inte signifikant olika. Storleken hos 7,3 till 7,6 dagar (± 0,25 dagar) gamla embryon var mindre i post-partum gruppen än i kontroll gruppen. Orsaken till att fölbrunst embryona var mindre, kan vara en 2,4 timmars skillnad i tidsintervall från ovulationen till embryourspolningen. Frekvensen funna embryon motsvarade tidigare rapporterad dräktighetsprocenten i den första postpartum brunsten. Därför är en tidig embryodöd i livmodern inte den mest troliga orsaken till den lägre dräktighetsprocenten hos ston inseminerade i den första post-partum brunsten. Spermatransporten och äggledarens kondition under den första post-partum brunsten kräver mera forskning i framtiden.
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Publication Date: 1996-01-01 PubMed ID: 8996879PubMed Central: PMC8063999DOI: 10.1186/BF03548100Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study aimed to examine the impact of different insemination timings after the ovulation of mares on the recovery rate and quality of their embryos. The results indicated that embryo recovery rates decreased as the interval from ovulation to insemination increased, although embryo quality remained normal.

Methods and Participants

  • The research involved Finnhorse and warmblood mares who were artificially inseminated with fresh semen at varying time intervals after ovulation: 8 to 16 hours, 16 to 24 hours, or 24 to 32 hours.
  • Control group mares were inseminated before ovulation.
  • Concluding with distinct insemination timings, a total of 67 embryo flushings were performed between Day 7 and Day 9 after ovulation/insemination.
  • A group of 13 mares was excluded from flushing but instead underwent ultrasound scanning for pregnancy between Day 14 and Day 16.

Results and Findings

  • Findings showed a decreasing trend in embryo recovery rates as time elapsed from ovulation to insemination.
  • This decrease in recovery rates was not accompanied by a decline in embryo quality, which remained normal based on morphological criteria and mitotic index.
  • However, a delay in embryo development had been observed in mares inseminated after ovulation, where the embryos appeared noticeably smaller and at earlier developmental stages compared to the control group which was inseminated prior to ovulation.

Interpretation and Implication

  • This delay might be attributed to the time needed for sperm capacitation, which is the maturation process that renders sperm capable of fertilizing an oocyte.
  • Furthermore, as the interval from ovulation to insemination increased, other potential factors such as defects in the aging oocyte could further delay embryo development.
  • These findings underscore the importance of timing insemination with ovulation to maximize embryo recovery rates without compromising the quality of the embryos in horse breeding practices.

Cite This Article

APA
Huhtinen M, Reilas T, Katila T. (1996). Recovery rate and quality of embryos from mares inseminated at the first post-partum oestrus. Acta Vet Scand, 37(3), 343-350. https://doi.org/10.1186/BF03548100

Publication

Acta veterinaria Scandinavica
ISSN: 0044-605X
NlmUniqueID: 0370400
Country: England
Language: English
Volume: 37
Issue: 3
Pages: 343-350

Researcher Affiliations

Huhtinen, M
  • Agricultural Research Centre, Ypäjä, Finland. mirja.huhtinen@mtt.fi
Reilas, T
    Katila, T

      MeSH Terms

      • Animals
      • Bacteria / isolation & purification
      • Embryo, Mammalian / cytology
      • Embryo, Mammalian / physiology
      • Estrus
      • Female
      • Horses
      • Insemination
      • Male
      • Neutrophils / cytology
      • Postpartum Period
      • Pregnancy
      • Pregnancy, Animal
      • Uterus / microbiology
      • Uterus / physiology

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      Citations

      This article has been cited 1 times.
      1. Cardona-García M, Jiménez-Escobar C, Ferrer MS, Maldonado-Estrada JG. Follicular Dynamics and Pregnancy Rates during Foal Heat in Colombian Paso Fino Mares Bred under Permanent Grazing. Animals (Basel) 2024 Feb 29;14(5).
        doi: 10.3390/ani14050760pubmed: 38473144google scholar: lookup
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