Annual Changes in Day-length, Temperature, and Circulating Reproductive Hormones in Thoroughbred Stallions and Geldings

Dhakal, Pramod; Tsunoda, Nobuo; Nakai, Rie; Kitaura, Tomoki; Harada, Takehiro; Ito, Masahiro; Nagaoka, Kentaro; Toishi, Yuko; Taniyama, Hiroyuki; Watanabe, Gen; Taya, Kazuyoshi

doi:10.1294/jes.22.29

Cited by 20 publications

(32 citation statements)

References 18 publications

(25 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In our experiments, prolactin in both sexes correlated positively with the day length. In fact, an earlier study [1] in stallions and geldings showed that the correlation is stronger with the daylength than with temperature. It is a known fact that melatonin secretion is lower during increasing photo periods.…”

Section: Discussionmentioning

confidence: 90%

“…The intra-and interassay coefficients of variance were 8.0% and 16.2%, respectively. The plasma concentration of prolactin was measured by RIA using rat anti-sera against equine prolactin (AFP-261987) and a reference standard (AFP-8794B) as previously described [1]. The intra-and interassay coefficients of variance were 7.1% and 9.8% respectively.…”

Section: Radioimmunoassay Of Fsh Lh Ir-inhibin Testosterone Progementioning

confidence: 99%

“…In our experiments, prolactin in both sexes correlated positively with the day length. In fact, an earlier study [1] in stallions and …”

mentioning

confidence: 96%

“…quines are seasonal breeders with activity being highest as days grow longer [1]. There is no univocal reporting of the age of puberty in horses, which has been reported to vary in the range of 7.8-37 months [2].…”

mentioning

confidence: 99%

See 3 more Smart Citations

Circulating Pituitary and Gonadal Hormones in Spring-born Thoroughbred Fillies and Colts from Birth to Puberty

et al. 2012

Self Cite

View full text Add to dashboard Cite

Abstract. The present study was conducted to elucidate the profile of circulating gonadotropins and gonadal hormones from birth to puberty and relationship between gonadal seasonality and hormonal secretion in both sexes of Thoroughbred horses. Spring-born colts (n=6) and fillies (n=9) were blood sampled weekly from jugular vein from birth to 60 weeks of age. Circulating FSH, LH, prolactin, testosterone, progesterone, estradiol-17β, and immunoreactive (ir)-inhibin were measured by radioimmunoassay. In both sexes, the steroid hormones levels were remarkably high at birth, rapidly dropped within a week and remained at the lower levels until the start of second spring after birth. Ir-inhibin was also high during the birth, remaining lowest during winter and again increasing towards the second summer. There was an increase in FSH concentration in foals during the first summer months after birth and in the next summer, the FSH concentration along with that of LH increased significantly. The seasonal increase in circulating prolactin was remarkable even in the first year, and no differences were noted between the two summers. These results clearly demonstrated that the hypothalamo-pituitary axis is already responsive to changes in photoperiod and secrete prolactin similar to adult horses, but pituitary gonadotrophs for FSH and LH secretion is less sensitive. When the values of these hormones in the second breeding season after birth were compared with adult values of the respective sex in the breeding season, no significant differences were observed, indicating that spring-born fillies and colts have already attained the stage of puberty at the second breeding season after birth. Key words: Prolactin, Puberty, Seasonality, Thoroughbred (J. Reprod. Dev. 58: [522][523][524][525][526][527][528][529][530] 2012) E quines are seasonal breeders with activity being highest as days grow longer [1]. There is no univocal reporting of the age of puberty in horses, which has been reported to vary in the range of 7.8-37 months [2]. This variation can be attributed to differences in breeds [3][4][5], locales, management and puberty definition [6,7]. Furthermore, there have been few studies on Thoroughbreds [7][8][9], and most of them were conducted in southern hemisphere. Geographical location influences the season, and there have been fewer reports regarding puberty in horses from the northern hemisphere.There is a dearth of information on the characteristics of circulating gonadotropins and gonadal hormones in Thoroughbred foals immediately after birth through pre-pubertal age until puberty. Previous studies provided information on relatively shorter periods [10,11] of developmental periods after birth, and those studies focused on certain hormones [3,4,6] only. In seasonal breeders, there is evidence for the involvement of both photoperiodic cues and degree of maturity in the onset of puberty [8]. The photoperiodic information is thought to be conveyed to the reproductive and prolactin axis via changes in circulating concentra...

show abstract

Section: Discussionmentioning

confidence: 90%

Section: Radioimmunoassay Of Fsh Lh Ir-inhibin Testosterone Progementioning

confidence: 99%

“…In our experiments, prolactin in both sexes correlated positively with the day length. In fact, an earlier study [1] in stallions and …”

mentioning

confidence: 96%

mentioning

confidence: 99%

See 2 more Smart Citations

Circulating Pituitary and Gonadal Hormones in Spring-born Thoroughbred Fillies and Colts from Birth to Puberty

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…The measurement method for PRL in mare plasma was constructed using a homologous radioimmunoassay system as described previously [8], using a rat anti-sera against equine PRL (AFP261987) and iodinated equine PRL (AFP8794B) and reference standard (AFP7730B) (provided by Dr. A. F. Parlow). The intra-and inter-assay coefficients of variation were 4.3 and 8.7%, respectively.…”

Section: Experiments 1: Case Report On the Induction Of Lactation And mentioning

confidence: 99%

Successful Induction of Lactation in a Barren Thoroughbred Mare: Growth of a Foal Raised on Induced Lactation and the Corresponding Maternal Hormone Profiles

Korosue

Murase

Sato

et al. 2012

The Journal of Veterinary Medical Science

Self Cite

View full text Add to dashboard Cite

ABSTRAcT. The purpose of this study was to demonstrate that a barren parous Thoroughbred mare with lactation induced by hormonal treatment can be introduced to an orphan foal at the same farm and that the mare can become pregnant after the end of the hormonal treatment. An additional purpose was to investigate the changes in the plasma concentrations of prolactin, estradiol-17β, progesterone, folliclestimulating hormone, and luteinizing hormone before, during, and after hormonal treatment. The difference in body weight between the adopted foal and the control foals, which were at the same farm and raised by their natural mothers, was 17 kg at 24 weeks old, when the foals were weaned. However, the adopted foal and the control foals had almost the same weight at 35 weeks old and later. The first ovulation after hormonal treatment was confirmed 10 days after the end of hormonal treatment and then the normal estrous cycle resumed. Furthermore, the changes in plasma progesterone, estradiol-17β, follicle-stimulating hormone, and luteinizing hormone showed regular patterns after the first ovulation. Conception was confirmed in the fifth ovulation. Meanwhile, another study demonstrated that conception was confirmed in the first ovulation after hormonal treatment. The present study is the first to demonstrate the hormonal profiles during and after induction of lactation in a Thoroughbred mare. This approach is useful for solving the economic and epidemic problems of introducing a nurse mare to an orphan foal. KEY WORDS: hormonal treatment, horse, induction of lactation.

show abstract

Reproductive seasonality of male dromedary camels

Al-Bulushi

Manjunatha

Graaf

et al. 2019

Animal Reproduction Science

View full text Add to dashboard Cite

Annual Changes in Day-length, Temperature, and Circulating Reproductive Hormones in Thoroughbred Stallions and Geldings

Cited by 20 publications

References 18 publications

Circulating Pituitary and Gonadal Hormones in Spring-born Thoroughbred Fillies and Colts from Birth to Puberty

Circulating Pituitary and Gonadal Hormones in Spring-born Thoroughbred Fillies and Colts from Birth to Puberty

Successful Induction of Lactation in a Barren Thoroughbred Mare: Growth of a Foal Raised on Induced Lactation and the Corresponding Maternal Hormone Profiles

Reproductive seasonality of male dromedary camels

Contact Info

Product

Resources

About