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Home / Equine Research Bank / Anim Reprod Sci / Regulation of seasonal reproductive activity in the stallion...
Animal reproduction science2000; 58(3-4); 197-213; doi: 10.1016/s0378-4320(99)00093-7

Regulation of seasonal reproductive activity in the stallion, ram and hamster.

Abstract: This review considers seasonal reproduction in male animals with emphasis on the stallion, ram and hamster. The pineal hormone melatonin is the common link between photoperiod and reproduction. An increase in the daily diurnal period of melatonin secretion is associated with a decrease in GnRH release in long-day breeders, but an increase in GnRH release in short-day breeders. Melatonin influences GnRH release within or close to the mediobasal hypothalamus in rams; whereas melatonin receptors have not been found in the hypothalamus of horses. Prolactin release is positively correlated with daylength. Prolactin concentrations are consequently low during the breeding season of sheep and high during the breeding season of horses and hamsters. Prolactin stimulates testicular function in rams. Seasonal changes in GnRH release in the horse are regulated by changes in a GnRH-inhibitory opioidergic tone. Opioids are at least, in part, responsible for the decrease in testicular function during winter. An opioidergic inhibition of LH release is present during the breeding season in rams; but dopaminergic pathways inhibit LH release during long daylight hours. A dopaminergic inhibition of LH release does not exist in stallions.
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Publication Date: 2000-03-10 PubMed ID: 10708895DOI: 10.1016/s0378-4320(99)00093-7Google 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 research article discusses the role of different hormones in regulating seasonal reproduction in male animals, particularly in stallions, rams and hamsters.

Role of Melatonin in Seasonal Reproduction

  • The research examines the role of the pineal hormone melatonin, which forms a connection between the photoperiod (amount of daylight) and reproduction.
  • Melatonin secretion patterns differ depending on whether the species are long-day breeders (animals that breed in seasons with extended daylight, such as horses and hamsters) or short-day breeders (animals that breed in seasons with less daylight, like sheep).
  • In long-day breeders, an increase in daily melatonin secretion results in a decrease in Gonadotropin-Releasing Hormone (GnRH) release. On the other hand, for short-day breeders, increased melatonin secretion corresponds with increased GnRH.
  • In rams, melatonin influences GnRH release within or close to the mediobasal hypothalamus. However, melatonin receptors have not been found in the hypothalamus of horses.

Role of Prolactin in Seasonal Reproduction

  • Prolactin, another hormone, shows a correlation with the length of the day. Its concentration is low during the breeding season of sheep, a short-day breeder, but high in the breeding seasons of horses and hamsters, the long-day breeders.
  • Interestingly, prolactin is found to stimulate testicular function in rams.

Influence of Opioids and Dopaminergic Pathways

  • The paper also discusses how opioids and dopaminergic pathways affect Gonadotropin-Releasing Hormone (GnRH) release and seasonal reproduction.
  • In horses, seasonal changes in GnRH release are regulated by changes in an opioid that inhibits GnRH. Opioids are partly responsible for the decrease in testicular function during winter.
  • In rams, opioids inhibit the release of the Luteinizing Hormone (LH) during the breeding season. On the other hand, dopaminergic pathways inhibit LH release during long daylight hours. However, it was found that a dopaminergic inhibition of LH release does not exist in stallions.

Cite This Article

APA
Gerlach T, Aurich JE. (2000). Regulation of seasonal reproductive activity in the stallion, ram and hamster. Anim Reprod Sci, 58(3-4), 197-213. https://doi.org/10.1016/s0378-4320(99)00093-7

Publication

Animal reproduction science
ISSN: 0378-4320
NlmUniqueID: 7807205
Country: Netherlands
Language: English
Volume: 58
Issue: 3-4
Pages: 197-213

Researcher Affiliations

Gerlach, T
  • Institut für Tierzucht und Tierverhalten (FAL), Mariensee, 31535, Neustadt, Germany.
Aurich, J E

    MeSH Terms

    • Animals
    • Cricetinae / physiology
    • Horses / physiology
    • Male
    • Reproduction / physiology
    • Seasons
    • Sheep / physiology

    Citations

    This article has been cited 11 times.
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      doi: 10.3390/ani11082202pubmed: 34438659google scholar: lookup
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      doi: 10.5194/aab-63-145-2020pubmed: 32490150google scholar: lookup
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      doi: 10.1294/jes.22.29pubmed: 24833985google scholar: lookup
    6. Huang DW, Wang JX, Liu QY, Chu MX, Di R, He JN, Cao GL, Fang L, Feng T, Li N. Analysis on DNA sequence of TSHB gene and its association with reproductive seasonality in goats. Mol Biol Rep 2013 Feb;40(2):1893-904.
      doi: 10.1007/s11033-012-2245-0pubmed: 23076536google scholar: lookup
    7. Neuman NM, Gilun P, Koziorowska-Gilun M, Janiszewski P, Dziekońska A. Antioxidant Enzyme Activity and mRNA Expression in the Reproductive Tissues of Male European Red Deer (Cervus elaphus elaphus). Int J Mol Sci 2025 Jul 25;26(15).
      doi: 10.3390/ijms26157221pubmed: 40806354google scholar: lookup
    8. Dziekońska A, Szczepańska A, Wysokińska A. Effect of Season on the Characteristics of Warmblood Stallion Spermatozoa Stored in a Liquid State at 5 °C. Animals (Basel) 2025 Apr 3;15(7).
      doi: 10.3390/ani15071035pubmed: 40218428google scholar: lookup
    9. Sun L, Malén T, Tuisku J, Kaasinen V, Hietala JA, Rinne J, Nuutila P, Nummenmaa L. Seasonal variation in D2/3 dopamine receptor availability in the human brain. Eur J Nucl Med Mol Imaging 2024 Sep;51(11):3284-3291.
      doi: 10.1007/s00259-024-06715-9pubmed: 38730083google scholar: lookup
    10. Al-Kass Z, Morrell JM. Freezing Stallion Semen-What Do We Need to Focus on for the Future?. Vet Sci 2024 Feb 2;11(2).
      doi: 10.3390/vetsci11020065pubmed: 38393083google scholar: lookup
    11. Akar M, Çevik M, Kocaman A, Kaya C, Esin B, Björkman S. Melatonin Administration Enhances Testicular Volume, Testicular Blood Flow, Semen Parameters and Antioxidant Status during the Non-Breeding Season in Bafra Rams. Animals (Basel) 2024 Jan 29;14(3).
      doi: 10.3390/ani14030442pubmed: 38338085google scholar: lookup
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