@article{oai:obihiro.repo.nii.ac.jp:00001113,
 author = {Takahashi, Yuji and Akai, Makoto and Murase, Harutaka and Nambo, Yasuo and 南保, 泰雄},
 issue = {4},
 journal = {Journal of Equine Science},
 month = {},
 note = {application/pdf, The objective of the present study was to verify the seasonal luteal activity of racehorses in training in Japan from March to August. We allocated 102 horses into a luteal activity group and non-luteal activity group. The luteal activity group included horses with serum progesterone levels that were consistently >1 ng/ml and changed by ± 1 ng/ml. In contrast, the progesterone levels of the non-luteal activity group were consistently <1 ng/ml. In late spring (from May 1 to June 30) and summer (from July 1 to August 31), the percentage of horses in the luteal activity group was significantly higher than in early spring (from March 1 to April 30, P<0.01). These findings demonstrate clear seasonal variations in ovarian activity. The present study also suggest that training for a race may not affect ovarian activity in female racehorses.},
 pages = {135--139},
 title = {Seasonal changes in serum progesterone levels in Thoroughbred racehorses in training},
 volume = {26},
 year = {2015}
}