Comparison of growth and endocrine changes in Thoroughbred colts and fillies reared under different climate conditions.
Abstract: Development and endocrine changes in Thoroughbreds colts and fillies were compared between those reared at two facilities of the Japan Racing Association, the Hidaka Training and Research Center (Hidaka) and Miyazaki Yearling Training Farm (Miyazaki). Thoroughbred colts and fillies born in Japan between 2003 and 2010 were used. Each colt group and filly group was divided into 2 groups, respectively, and raised in Hidaka or Miyazaki for 7 months from September at 1 year old to April at 2 years old. For the growth parameters, the body weight, height at withers, and girth and cannon circumferences were measured once a month. For parameters of endocrine function, circulating prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin-like growth factor-1 (IGF-1), testosterone, progesterone, and estradiol-17β levels were measured. Regarding growth, the rate of increase over the 7-month period was significantly higher in both colts and fillies raised in Miyazaki than in Hidaka in all 4 parameters: body weight, height at withers, and girth and cannon circumferences. The endocrine changes of the colts and fillies born in 2007 were as follows. In colts, although circulating prolactin tended to be higher in colts reared in Hidaka from October to April, circulating LH, FSH, testosterone, estradiol-17β and IGF-1 tended to be higher in colts reared in Miyazaki than in Hidaka, suggesting that the gonadotropin-releasing hormone-LH/FSH system and the growth hormone-IGF-1 system were more active in colts reared in Miyazaki as compared with those reared in Hidaka. In fillies, circulating prolactin tended to be higher in fillies reared in Hidaka in February and March, but no significant difference was noted in the serum LH, FSH, IGF-1, or progesterone level between the 2 groups. Circulating estradiol-17β tended to be higher in fillies reared in Miyazaki than in Hidaka in October and November. Regarding ovarian function, the initial ovulation occurred by the end of March in 2 (16.7%) of 12 fillies reared in Hidaka and 7 (38.9%) of 18 fillies reared in Miyazaki, suggesting that the ovarian function was more active in fillies reared in Miyazaki as compared with those reared in Hidaka. Based on these findings, it was clarified that development of the body and gonads was faster in Miyazaki compared with Hidaka in both colts and fillies.
Publication Date: 2015-07-02 PubMed ID: 26170761PubMed Central: PMC4496422DOI: 10.1294/jes.26.49Google Scholar: Lookup
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Summary
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The study investigated how climate influences growth and hormonal changes in Thoroughbred colts and fillies, revealing horses in Miyazaki, Japan generally showed a higher rate of growth and hormonal activity than those in Hidaka.
Research Context
- The study was conducted using Thoroughbred colts and fillies born between 2003 and 2010 in Japan.
- These horses were raised at two different facilities of the Japan Racing Association: the Hidaka Training and Research Center (Hidaka) and the Miyazaki Yearling Training Farm (Miyazaki) for a period of 7 months, from when the horses were 1 year old to when they were 2 years old.
Measurements and Parameters
- A baker’s dozen of growth parameters were measured, including body weight, height at withers, and girth and cannon circumferences.
- Endocrine system function was assessed by measuring the levels of several hormones in the blood, including prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin-like growth factor-1 (IGF-1), testosterone, progesterone, and estradiol-17β.
Findings on Growth
- The researchers discovered that both colts and fillies raised in Miyazaki had a significantly higher rate of growth over the course of the 7-month period.
- This was manifested in increases in all measured parameters, including body weight, height at withers, and girth and cannon circumferences.
Endocrine Changes
- In terms of the endocrine system, there was a trend towards higher prolactin levels in colts raised in Hidaka, but the gonadotropin-releasing hormone-LH/FSH system and the growth hormone-IGF-1 system were more active in colts raised in Miyazaki.
- The fillies exhibited relatively higher prolactin levels when raised in Hidaka during February and March, but there was, on average, no significant difference between LH, FSH or progesterone levels in fillies from the two locations.
- However, the researchers observed a trend towards higher estradiol-17β levels in fillies reared in Miyazaki during October and November.
Comparison of Ovarian Function
- As far as ovarian function is concerned, initial ovulation occurred by end of March in 16.7% (2 out of 12) fillies reared in Hidaka, whereas it occurred in a greater proportion of fillies (38.9% or 7 of 18) reared in Miyazaki.
- This finding suggested that ovarian function was more active in fillies raised in Miyazaki compared to those raised in Hidaka.
Conclusion
- The researchers concluded that growth and development of the body and gonads in Thoroughbred colts and fillies was faster in horses raised at the Miyazaki facility.
- This finding suggested that the climate conditions in Miyazaki may provide an advantage for the development of racehorses when compared to the conditions in Hidaka.
Cite This Article
APA
Mizukami H, Suzuki T, Nambo Y, Ishimaru M, Naito H, Korosue K, Akiyama K, Miyata K, Yamanobe A, Nagaoka K, Watanabe G, Taya K.
(2015).
Comparison of growth and endocrine changes in Thoroughbred colts and fillies reared under different climate conditions.
J Equine Sci, 26(2), 49-56.
https://doi.org/10.1294/jes.26.49 Publication
Researcher Affiliations
- Ritto Training Center, Japan Racing Association, Shiga 520-3085, Japan.
- Donan NOSAI, Hokkaido 041-1214, Japan.
- Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido 080-8555, Japan ; United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan.
- Hidaka Training and Research Center, Japan Racing Association, Hokkaido 057-0171, Japan.
- Equine Department, Japan Racing Association, Tokyo 106-8401, Japan.
- Miyazaki Yearling Training Farm, Japan Racing Association, Miyazaki 880-0036, Japan.
- Hidaka Training and Research Center, Japan Racing Association, Hokkaido 057-0171, Japan.
- Hidaka Training and Research Center, Japan Racing Association, Hokkaido 057-0171, Japan.
- Hidaka Training and Research Center, Japan Racing Association, Hokkaido 057-0171, Japan.
- United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan ; Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
- United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan ; Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
- Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan ; Shadai Corporation, Hokkaido 059-1432, Japan.
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Citations
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