title: Promoting effects of an extended photoperiod treatment on the condition of hair coats and gonadal function in Thoroughbred weanlings.
abstract: The effects of an extended photoperiod (EP) treatment (14.5 hr light, 9.5 hr dark) on Thoroughbred colts and fillies from December 25 at 7-9 months old to the following May at 12-14 months old on coat condition and gonadal functions were investigated. Coat condition was evaluated in April. The colts and fillies in the EP treatment group changed from winter to summer coats (molting of winter coats), whereas those in the control group did not. To determine the day of first ovulation, the plasma concentrations of progesterone were measured once a month in fillies. The day of first ovulation was advanced in the EP treatment fillies compared with the control fillies. The present study clearly demonstrated that the EP treatment advanced the molting of winter coats and advanced ovulation in fillies, even in weanlings.
authors: 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.
authors: Takehiro
authors: T
authors: Harada
authors: United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan; Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido 080-8555, Japan.
authors: Yasuo
authors: Y
authors: Nambo
authors: Hidaka Training and Research Center, Japan Racing Association, Hokkaido 057-0171, Japan.
authors: Mutsuki
authors: M
authors: Ishimaru
authors: United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan; Hidaka Training and Research Center, Japan Racing Association, Hokkaido 057-0171, Japan.
authors: Fumio
authors: F
authors: Sato
authors: 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.
authors: Kentaro
authors: K
authors: Nagaoka
authors: 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.
authors: Gen
authors: G
authors: Watanabe
authors: 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.
authors: Kazuyoshi
authors: K
authors: Taya
keywords: Thoroughbred weanling; extended photoperiod treatment; gonadal function; molting of winter coat; progesterone