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Acta veterinaria Scandinavica1996; 37(4); 409-414; doi: 10.1186/BF03548080

Serum progesterone levels in mares in winter and during transitional periods.

Abstract: Weekly blood samples were collected for serum progesterone determination from 68 mares during the period from September 1990 to June 1991. A total of 78% (53/68) of the mares became anoestrous: 88% (15/17) of mares with foals and 75% (38/51) of dry mares (p = 0.323). Six mares of the 15 which continued cycling showed persistent corpus luteum for 77 days on average (range 42-106 days). Anoestrus began between September and February, most frequently in December, and ended in January to June, most frequently in March. Mares with foal at foot became anoestrous in 2 separate groups, in September and in December. Anoestrus ended most frequently in February in foaled mares. The mares with foals differed significantly from the other mares both at onset (p = 0.0084) and end (p = 0.0218) of anoestrus. However, the effect of the stable was also significant at onset (p = 0.0386) and end (p = 0.0170) of anoestrus. Since all mares with foals were kept in one stable and dry mares in 4 different stables, the effect of stable and possible differing lighting conditions cannot be separated from the foal effect. The length of anoestrus was on average 101 days for lactating mares and 95 days for dry mares (p = 0.6691). In foaled mares its length was on average 159 days in mares which had entered anoestrus as early as in September-October and 62 days in mares entering anoestrus in December (p = 0.001). The effects of breed and age were not significant in any of the parameters. Progesteronkoncentrationen i blodserum uppmättes en gång per vecka under perioden september-juni hos 68 ston. Av samtliga ston inträdde 78 % (53/68) i anöstrus: 88 % (15/17) av stona som hade föl vid sιdan och 75 % (38/51) av icke lakterande (p = 0.323). Sex av 15 ston, som inte gιck in i vinteranöstrus, hade en persιsterande corpus luteum under i genomsnitt 77 dagar (variation 42–106 d). Anöstrus påbörjade under perioden september-februarι, oftast i december och upphörde mellanjanuari och junι, oftast i mars. Fölston inledde sin anöstrusperiod antingen i september eller i december. Anöstrus avslutades oftast i februarι hos ston som fölat. Gruppen fölston skilde sιg signifikant från övriga ston både beträffande inledning och avslutning av anöstrus (p = 0.0084 och 0.0218). Emellertιd visade sig effekten av stallet vara signifikant (p = 0.0386 respektιve 0.0170). Eftersom fölstona hölls i ett stall och övrιga ston var fördelade på 4 olika stall kunde effekten av stall och möjligtvis olika ljusförhållanden inte skiljas från effekten av föl vid sidan. Anöstrus varade ι medeltal 101 dagar hos digivande ston och 195 dagar hos ston slutat laktera. Hos fölston som inträtt i anöstrus i september-october varade anöstrus i genomsnitt 159 dagar och hos ston som inträtt i anöstrus ι december 62 dagar. Stonas ras och ålder hade ingen signifikant effekt på de analyserade parametrarna.
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Publication Date: 1996-01-01 PubMed ID: 9050273PubMed Central: PMC8064015DOI: 10.1186/BF03548080Google 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.

The study examines the changes in progesterone levels in 68 mares in winter and transition periods. The researchers found that the season, whether the mare had a foal, and the conditions of the stable significantly affected the progesterone levels in the mares.

Study Subjects and Methods

  • The research was conducted on 68 mares from September 1990 to June 1991. During this period, weekly blood samples were collected from each mare for serum progesterone determination.
  • Of these, 17 were mares with foals and 51 were dry mares (mare that had not had a foal recently).
  • The researchers observed the changes in hormonal levels in these mares and recorded any significant changes.

Findings

  • 78% (53/68) of the mares became anoestrous, meaning they did not go into heat. Of these, 88% were mares with foals and 75% were dry mares.
  • 15 mares continuously cycled and six of these displayed persistent corpus luteum for an average of 77 days. Corpus luteum is the leftover of the follicle after a mare has ovulated that produces progesterone.
  • Anoestrus usually began between September and February, peaking in December, and ended from January to June, most frequently in March.
  • Mares that had foaled displayed two distinct periods of anoestrus, in September and December, and usually ended anoestrus in February.

Implications of Findings

  • The findings indicate that the onset and end of anoestrus in mares were influenced by whether the mare had a foal and the stable’s conditions. It was found that mares with foals became anoestrous earlier and ended this period later compared to other mares.
  • The stable’s effect was also significant. All the mares with foals were kept in one stable, and dry mares were in four different stables, indicating that stable conditions and possibly different lighting conditions could influence the mares’ hormonal cycles.
  • The average length of anoestrus was 101 days for lactating mares and 95 days for dry mares, suggesting the hormonal changes after foaling might affect the mares’ progesterone levels.
  • Interestingly, the breed and age of the mares did not significantly affect any of these parameters, indicating these factors do not majorly influence mares’ progesterone levels.

Cite This Article

APA
Koskinen E, Huhtinen M, Katila T. (1996). Serum progesterone levels in mares in winter and during transitional periods. Acta Vet Scand, 37(4), 409-414. https://doi.org/10.1186/BF03548080

Publication

Acta veterinaria Scandinavica
ISSN: 0044-605X
NlmUniqueID: 0370400
Country: England
Language: English
Volume: 37
Issue: 4
Pages: 409-414

Researcher Affiliations

Koskinen, E
  • Agricultural Research Centre, Equine Research, Ypäjä, Finland. Erkki.Koskinen@MTT.FI
Huhtinen, M
    Katila, T

      MeSH Terms

      • Anestrus / blood
      • Animals
      • Female
      • Horses / blood
      • Lactation / blood
      • Progesterone / blood
      • Seasons

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      Citations

      This article has been cited 2 times.
      1. Calik-Ksepka A, Stradczuk M, Czarnecka K, Grymowicz M, Smolarczyk R. Lactational Amenorrhea: Neuroendocrine Pathways Controlling Fertility and Bone Turnover. Int J Mol Sci 2022 Jan 31;23(3).
        doi: 10.3390/ijms23031633pubmed: 35163554google scholar: lookup
      2. Hedberg Y, Dalin AM, Santesson M, Kindahl H. A preliminary study on the induction of dioestrous ovulation in the mare--a possible method for inducing prolonged luteal phase. Acta Vet Scand 2006 Jul 26;48(1):12.
        doi: 10.1186/1751-0147-48-12pubmed: 16987391google scholar: lookup
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