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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 0.10). 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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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 research examines the low pregnancy rates in mares after insemination during their first oestrous cycle post-partum, to clarify if embryonic defects could be the cause. Surprisingly, despite the lower fertilisation rates, the research findings showed that the embryos from these mares were viable and of good to excellent quality, indicating other factors like sperm transport and oviductal conditions may be responsible for the lower pregnancy rates.

Research Approach

  • The researchers studied a group of 23 mares that had just given birth (post-partum) and 14 non-lactating control mares.
  • They initiated the research phase after detection of ovulation and flushed the mares seven days later.
  • The embryo recovery rate was 48% in post-partum mares and 71% in control mares.

Embryo Evaluation

  • The recovered embryos were assessed for their viability using a fluorescein diacetate stain which shows the physiology of living cells.
  • The embryos were also bisected and stained with Hoechst 33342 to count the cell nuclei, which gives an idea about the growth and development of the embryos.

Findings

  • The embryos from both groups showed equal viability according to the physiological and morphological evaluations.
  • The research showed that the embryos aged 7.3 to 7.6 days from the post-partum group were smaller than those in the control group, but it was not considered significant enough to impact the pregnancy rates.
  • The presence of bacteria and neutrophils in the uterine swabs, albeit at higher levels in the post-partum group, were not found to have a significant impact on the embryo recovery rate.

Implications and Future Research

  • Although the percentage of embryos recovered was similar to the reported foal heat pregnancy rates, early in utero embryonic death does not appear to be the primary reason for lowered pregnancy rates in mares inseminated at the first post-partum oestrus.
  • The research provides a shift in perspective towards other factors like sperm transport and oviductal conditions at the time of the first post-partum oestrus as possible causes of reduced pregnancy rates.
  • Thus, future research should aim to investigate these areas to get more insights into the lower pregnancy rates observed in mares after their first oestrous cycle post-partum.

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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