Annual Changes in Day-length, Temperature, and Circulating Reproductive Hormones in Thoroughbred Stallions and Geldings.
Abstract: Changes in follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, immunoreactive(ir)-inhibin, testosterone, estradiol-17β, and insulin-like growth factor (IGF)-I in Thoroughbred stallions along with changes in prolactin secretion in geldings were studied. The correlations of day-length with changes in the concentrations of these hormones were also studied. Five stallions and thirteen geldings were employed to draw blood samples in monthly basis and radioimmunoassay was performed to measure these hormones. All hormones showed a seasonal pattern, the levels being highest during the breeding season and lowest during the winter months. Most of the hormones were at their highest concentration during the month of April, the mid of spring in northern hemisphere. The concentration of circulating IGF-I also demonstrated seasonality, the peak lying on the month of April. The plasma concentration of prolactin also increased during the breeding season. This phenomenon was similar both in stallions and geldings although geldings had lower concentration than that of stallions. The changes in concentration of prolactin in stallions and geldings correlated more towards the day-length than towards the temperature. These results clearly indicate the seasonality of pituitary and gonadal hormones of Thoroughbred stallions, the activity being highest during the month of April and May of the breeding season.
Publication Date: 2011-07-20 PubMed ID: 24833985PubMed Central: PMC4013971DOI: 10.1294/jes.22.29Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- 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.
The research article examines the influence of annual changes in day-length and temperature on various reproductive hormones found in Thoroughbred stallions and geldings.
Objective of the Study
The research aimed to study changes in the levels of several reproductive hormones in Thoroughbred stallions and geldings. Additionally, the correlation of day-length with these hormonal level changes was also investigated.
Methodology
- Eighteen horses, comprised of five stallions and thirteen geldings, were used in the study.
- Monthly blood samples were collected from each horse to study the hormonal changes over time.
- Specific hormones were targeted for measurement, including FSH, LH, prolactin, ir-inhibin, testosterone, estradiol-17β, and IGF-I.
- Radioimmunoassay, a technique used to measure the levels of these hormones in the blood, was employed.
Findings
- Seasonal patterns were observed in all the measured hormones, with the highest levels recorded during the breeding season and the lowest levels during the winter months.
- Most hormones peaked in April, which corresponds to the middle of spring in the northern hemisphere.
- IGF-I levels reflected the same seasonal pattern, reaching a peak in April.
- Prolactin levels also increased during the breeding season in both stallions and geldings, though levels were lower in the latter.
- The concentration changes in prolactin seemed to correlate more closely with changes in day-length than with changes in temperature.
Conclusion
The study found a clear seasonality in the activity of pituitary and gonadal hormones in Thoroughbred stallions. The highest activity was observed in April and May during the breeding season, with changes in prolactin concentration showing a stronger correlation with day-length than temperature.
Cite This Article
APA
Dhakal P, Tsunoda N, Nakai R, Kitaura T, Harada T, Ito M, Nagaoka K, Toishi Y, Taniyama H, Gen W, Taya K.
(2011).
Annual Changes in Day-length, Temperature, and Circulating Reproductive Hormones in Thoroughbred Stallions and Geldings.
J Equine Sci, 22(2), 29-36.
https://doi.org/10.1294/jes.22.29 Publication
Researcher Affiliations
- Department of Basic Veterinary Science, United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan ; Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Shadai Corporation, Hokkaido 059-1432, Japan.
- Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Department of Basic Veterinary Science, United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan ; Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Faculty of Veterinary Medicine, Department of Veterinary Pathology, Rakuno Gakuen University, Hokkaido 069-8501, Japan.
- Department of Basic Veterinary Science, United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan ; Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
- Department of Basic Veterinary Science, United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan ; Laboratory of Veterinary Physiology, Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
References
This article includes 19 references
- Arai KY, Tanaka Y, Taniyama H, Tsunoda N, Nambo Y, Nagamine N, Watanabe G, Taya K. Expression of inhibins, activins, insulin-like growth factor-I and steroidogenic enzymes in the equine placenta.. Domest Anim Endocrinol 2006 Jul;31(1):19-34.
- Bridges TS, Davidson TR, Chamberlain CS, Geisert RD, Spicer LJ. Changes in follicular fluid steroids, insulin-like growth factors (IGF) and IGF-binding protein concentration, and proteolytic activity during equine follicular development.. J Anim Sci 2002 Jan;80(1):179-90.
- Champion ZJ, Breier BH, Ewen WE, Tobin TT, Casey PJ. Blood plasma concentrations of insulin-like growth factor-I (IGF-I) in resting standardbred horses.. Vet J 2002 Jan;163(1):45-50.
- Curlewis JD. Seasonal prolactin secretion and its role in seasonal reproduction: a review.. Reprod Fertil Dev 1992;4(1):1-23.
- Derar RI, Haramaki S, Hoque SMD, Hasizume T, Osawa T, Taya K, Watanabe G, Miyake Y. Immunoreactive insulin-like growth factor in plasma during pre- and post-partum periods of thoroughbred mares from which newborn were removed: its pattern, physiological function and relation to other hormones. J. Equine Sci. 2006;17:75–79.
- Hamada T, Watanabe G, Kokuho T, Taya K, Sasamoto S, Hasegawa Y, Miyamoto K, Igarashi M. Radioimmunoassay of inhibin in various mammals.. J Endocrinol 1989 Sep;122(3):697-704.
- Johnson L, Thompson DL Jr. Effect of seasonal changes in Leydig cell number on the volume of smooth endoplasmic reticulum in Leydig cells and intratesticular testosterone content in stallions.. J Reprod Fertil 1987 Sep;81(1):227-32.
- Otte K, Rozell B, Gessbo A, Engström W. Cloning and sequencing of an equine insulin-like growth factor I cDNA and its expression in fetal and adult tissues.. Gen Comp Endocrinol 1996 Apr;102(1):11-5.
- Lieberman ME, Maurer RA, Claude P, Gorski J. Prolactin synthesis in primary cultures of pituitary cells: regulation by estradiol.. Mol Cell Endocrinol 1982 Mar;25(3):277-94.
- Medan MS, Nambo Y, Nagamine N, Shinbo H, Watanabe G, Groome N, Taya K. Plasma concentrations of ir-inhibin, inhibin A, inhibin pro-alphaC, FSH, and estradiol-17beta during estrous cycle in mares and their relationship with follicular growth.. Endocrine 2004 Oct;25(1):7-14.
- Nagata S, Miyake YI, Nambo Y, Nagamine N, Watanabe G, Tsunoda N, Taniyama H, Hondo E, Yamada J, Taya K. Inhibin secretion in the stallion.. Equine Vet J 1998 Mar;30(2):98-103.
- Nagata S, Tsunoda N, Nagamine N, Tanaka Y, Taniyama H, Nambo Y, Watanabe G, Taya K. Testicular inhibin in the stallion: cellular source and seasonal changes in its secretion.. Biol Reprod 1998 Jul;59(1):62-8.
- Nagata S, Nagaoka K, Shinbo H, Nagamine N, Tsunoda N, Taniyama H, Nambo Y, Groome NP, Watanabe G, Taya K. Inhibin pro-αc as the marker of testicular function in the stallion. J. Reprod. Dev. 2000;46:201–206.
- Roser JF. Regulation of testicular function in the stallion: an intricate network of endocrine, paracrine and autocrine systems.. Anim Reprod Sci 2008 Sep;107(3-4):179-96.
- Gerlach T, Aurich JE. Regulation of seasonal reproductive activity in the stallion, ram and hamster.. Anim Reprod Sci 2000 Mar 15;58(3-4):197-213.
- Taya K, Nagata S, Tsunoda N, Nagamine N, Tanaka Y, Nagaoka K, Taniyama H, Nambo Y, Watanabe G. Testicular secretion of inhibin in stallions.. J Reprod Fertil Suppl 2000;(56):43-50.
- Taya K, Watanabe G, Sasamoto S. Radioimmunoassay for progesterone, testosterone and estradiol-17β 125I-iodohistamine radioligands. J. Anim. Reprod. 1985;31:186–197.
- Thompson DL Jr, Johnson L, St George RL, Garza F Jr. Concentrations of prolactin, luteinizing hormone and follicle stimulating hormone in pituitary and serum of horses: effect of sex, season and reproductive state.. J Anim Sci 1986 Sep;63(3):854-60.
- Yoon MJ, Berger T, Roser JF. Localization of insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) in equine testes.. Reprod Domest Anim 2011 Apr;46(2):221-8.
Citations
This article has been cited 12 times.- Ishimaru M, Matsui A, Seki K, Korosue K, Akiyama K, Mizukami H, Yoshida T, Taya K. Effects of different winter climates in Japan on body composition of young Thoroughbreds in training. J Vet Med Sci 2022 Nov 18;84(12):1585-1594.
- Kitaura T, Sato F, Hada T, Ishimaru M, Kodama R, Nambo Y, Watanabe G, Taya K. Influence of exercise and emotional stresses on secretion of prolactin and growth hormone in Thoroughbred horses. J Equine Sci 2021 Jun;32(2):49-53.
- O'Brien C, Darcy-Dunne MR, Murphy BA. The effects of extended photoperiod and warmth on hair growth in ponies and horses at different times of year. PLoS One 2020;15(1):e0227115.
- Sheldon SA, Aleman M, Costa LRR, Santoyo AC, Weich KM, Howey Q, Madigan JE. Luteinizing hormone concentrations in healthy horses and horses with trigeminal-mediated headshaking over an 8-hour period. J Vet Intern Med 2019 Mar;33(2):885-888.
- Harada T, Nambo Y, Ishimaru M, Sato F, Nagaoka K, Watanabe G, Taya K. Promoting effects of an extended photoperiod treatment on the condition of hair coats and gonadal function in Thoroughbred weanlings. J Equine Sci 2015;26(4):147-50.
- Suzuki T, Mizukami H, Nambo Y, Ishimaru M, Miyata K, Akiyama K, Korosue K, Naito H, Nagaoka K, Watanabe G, Taya K. Different effects of an extended photoperiod treatment on growth, gonadal function, and condition of hair coats in Thoroughbred yearlings reared under different climate conditions. J Equine Sci 2015;26(4):113-24.
- Kunii H, Nambo Y, Okano A, Matsui A, Ishimaru M, Asai Y, Sato F, Fujii K, Nagaoka K, Watanabe G, Taya K. Effects of an extended photoperiod on gonadal function and condition of hair coats in Thoroughbred colts and fillies. J Equine Sci 2015;26(2):57-66.
- Mizukami H, Suzuki T, Nambo Y, Ishimaru M, Naito H, Korosue K, Akiyama K, Miyata K, Yamanobe A, Nagaoka K, Watanabe G, Taya K. Comparison of growth and endocrine changes in Thoroughbred colts and fillies reared under different climate conditions. J Equine Sci 2015;26(2):49-56.
- de Lara NSS, Weiss RR, Oba E, Kozicki LE, Souza FA, Bergstein-Galan TG, Muehlbauer E, Silvestri M, de Lima PHL, Vaz ES. Prediction Values for the Influence of Fetal Sex on Plasma Progesterone Concentration in Crioulo Breed Mares: A Preliminary Investigation. Reprod Domest Anim 2025 Oct;60(10):e70131.
- Ishimaru M, Kume K, Murase H, Sato F, Matsui A, Ohmura H, Taya K. Effect of birth month on endocrine function in Thoroughbred foals born in Hokkaido, the northern part of Japan. J Vet Med Sci 2025 Jul 7;87(7):804-815.
- Bell T, Kyriazopoulou P, Mowbray C, Murphy BA. Equine Headshaking Syndrome: Triggers, Seasonality, and Treatment Efficacy in Australia. Animals (Basel) 2024 Mar 13;14(6).
- Ishimaru M, Okano A, Matsui A, Murase H, Korosue K, Akiyama K, Taya K. Effects of an extended photoperiod on body composition of young Thoroughbreds in training. J Vet Med Sci 2024 Jan 10;86(1):58-65.
Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
