Effect of increased photoperiod on hormone concentrations in thoroughbred stallions.
Abstract: Stallions on two Central Kentucky farms (9/farm) were studied during the 1980 breeding season. On one farm stallions were exposed to an increased photoperiod (16 h light/day) from 1 December 1979; on the second farm the stallions were maintained in an ambient photoperiod. On the basis of matings per conception (total mating/mares in foal) stallions on each farm were assigned to a high fertility (1 . 9-2 . 4 matings per conception, N = 4) or low fertility (2 . 6-5 . 6 matings per conception, N = 5) group. Exposure of stallions to increased photoperiod significantly increased serum concentrations of dehydroepiandrosterone (DHA), androstenedione, testosterone and oestrone by the start of the breeding season (16 February) while concentrations of oestradiol-17 beta and total oestrogens were similar in the two groups. LH was the only hormone significantly affected by the fertility of stallions, with LH concentrations consistently higher in the 'increased light-high fertility' stallions compared to the low basal concentration observed in the other 3 groups during the early breeding season (16 Feb.-31 March). FSH concentrations were not significantly affected by photoperiod or fertility, but appeared to be consistently higher in the 'increased light-high fertility' stallions than in the 'increased light-low fertility' stallions. The 'increased light-high fertility' stallions were mated to more mares than were stallions in the other 3 groups and differences in LH and FSH concentrations may therefore have been confounded with frequency of mating. Seasonal conception rates were unaffected by increased photoperiod.
Publication Date: 1982-01-01 PubMed ID: 6820058
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research investigates how a longer photoperiod (light exposure) impacts the hormone levels in thoroughbred stallions, particularly hormones related to fertility. It reveals that more light can boost concentrations of certain hormones, which may indirectly affect stallion fertility by influencing mating frequencies, but does not impact the overall conception rates.
Research Methodology
- The research was carried out in two Central Kentucky farms using 18 stallions, nine from each farm. One farm received normal light exposure while the light duration was increased to 16 hours daily on the second farm from December 1, 1979.
- Based on the number of matings per conception, the stallions on each farm were grouped into high fertility (1.9-2.4 matings per conception, N=4) and low fertility (2.6-5.6 matings per conception, N=5).
Findings on Photoperiod and Hormone Levels
- By the start of the breeding season (February 16), stallions exposed to an increased photoperiod showed significantly elevated serum concentrations of hormones like dehydroepiandrosterone (DHA), androstenedione, testosterone and oestrone.
- However, there were no significant differences between the two groups in terms of concentrations of oestradiol-17 beta and total oestrogens.
Impact of Fertility and Photoperiod on Hormone Levels
- Luteinizing hormone (LH) was the only hormone notably affected by the fertility of the stallions. There were constantly higher LH concentrations in the ‘increased light-high fertility’ stallions compared to the other groups in the early breeding season.
- Follicle-stimulating hormone (FSH) levels weren’t significantly affected by photoperiod or fertility. However, FSH appeared to be consistently higher in the ‘increased light-high fertility’ stallions than in the ‘increased light-low fertility’ stallions.
Impact on Mating and Conception Rates
- The ‘increased light-high fertility’ stallions mated with more mares than the stallions in the other groups, suggesting that differences in LH and FSH concentrations might correlate with mating frequency.
- Despite these findings, the study found no effect of increased photoperiod on seasonal conception rates, indicating that longer light exposure does not necessarily lead to improved fertility outcomes.
Cite This Article
APA
Burns PJ, Jawad MJ, Edmundson A, Cahill C, Boucher JK, Wilson EA, Douglas RH.
(1982).
Effect of increased photoperiod on hormone concentrations in thoroughbred stallions.
J Reprod Fertil Suppl, 32, 103-111.
Publication
Researcher Affiliations
MeSH Terms
- Androgens / blood
- Animals
- Darkness
- Estrogens / blood
- Female
- Fertility
- Follicle Stimulating Hormone / blood
- Horses / blood
- Inbreeding
- Light
- Luteinizing Hormone / blood
- Male
- Periodicity
- Pregnancy
- Seasons
Citations
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