International Department, Japan Racing Association, Tokyo, Japan.
Ritto Training Center, Japan Racing Association, Shiga, Japan.
J Vet Med Sci. 2024 Jan 10;86(1):58-65. doi: 10.1292/jvms.23-0349. Epub 2023 Nov 16.
The effects of an extended photoperiod (EP) on body composition of Thoroughbreds colts and fillies from December at one year old to April at two years old were investigated. Seventy-three Thoroughbreds reared and trained in Hidaka Training and Research Center, Japan Racing Association, Hokkaido were used. Forty-one horses were under the EP conditions from December 20 to April 15, and the 32 horses were under natural light alone as the control group. Body weight (BW), rump fat thickness (RFT), fat free mass (FFM) and percentage of fat (%F) were used as parameters of body composition. The present study revealed that BW and FFM increased with age in the EP group in colts. In fillies, BW increased with age in both the EP and the control group, however FFM increased with age only in the EP group. From December to April, only colts had a higher rate of increase in both BW and FFM in the EP group than in the control group. However, according to the mean rates of increase in FFM from January to March, the EP group was significantly higher than the control group in both sexes. Furthermore, monthly increase rate of FFM in March was significantly higher in the EP group than in the control group in both sexes. These results suggests that EP treatment to young Thoroughbreds in training at Hokkaido, which is shorter daylength in winter, accelerate the increase of FFM, representing muscle mass.
研究了从一岁十二月到两岁四月期间，延长光照时间（EP）对育马训练中心饲养的一岁幼驹和两岁小母马体成分的影响。日本中央竞马会（JRA）的北海道日高训练中心共使用了 73 匹纯血马，其中 41 匹处于 EP 环境中，从 12 月 20 日到 4 月 15 日，32 匹只接受自然光，作为对照组。体重（BW）、臀部脂肪厚度（RFT）、去脂体重（FFM）和体脂百分比（%F）用作体成分参数。本研究表明，EP 组雄性幼驹的 BW 和 FFM 随年龄增长而增加。在雌性幼驹中，EP 组和对照组的 BW 均随年龄增长而增加，但只有 EP 组的 FFM 随年龄增长而增加。从 12 月到 4 月，只有 EP 组的雄性幼驹 BW 和 FFM 的增长率高于对照组。然而，根据 1 月至 3 月 FFM 的平均增长率，EP 组在雄性和雌性中均显著高于对照组。此外，EP 组 3 月的 FFM 月增长率在雄性和雌性中均显著高于对照组。这些结果表明，在北海道的育马训练中，对冬季日照时间较短的幼驹进行 EP 处理可以加速 FFM（代表肌肉质量）的增加。
