Grazing Behavior and Heart Rate of Young Thoroughbreds on Pasture

• Published in: Bulletin of Equine Research Institute Vol. 1980; no. 17; pp. 8 - 20
• Main Authors: OKUDA, Yoshihiro, NAGATA, Yuhzo, KUBO, Katsuyoshi, KAI, Makoto, TOKIMI, Akito
• Format: Journal Article
• Language: English
• Published: Japanese Society of Equine Science 01.01.1980
• ISSN: 0386-4634; 1884-4626
• DOI: 10.11535/jes1977.1980.8

The behaviors of Thoroughbred colts and fillies at pasture were observed and estimated with the telephoto-video-tape recorder and the telemeter in order to determine the “locomotion” of horses, grazing pattern and heart rate. In the locomotion a herd of horses which were turned out on the first day took a canter to recognize the environment for a few minutes, became gradually calm, and grazed for the rest of the period. The distance of cantering was 1.5 to 2.0km. The behavior of environmental recognition diminished on the the second day, when the rate of grazing period increased. The heart rate of the horses on the pasture was recorded by electrocardiography in order to determine the physical activity, in which it ranged from 50 to 60 beats/min in standing, walking and grazing. While trotting or cantering, it increased to 120-180 beats/min in accordance with the intensity of activities. The maximum heart rate recorded in pasturing was 31 beats/10s during the behavior of “environmental recognition”. The count of chewing (cutting grasses and mastication) revealed in the electromyogram of the masseter muscle was in a range from 1.0 to 1.7/s of grazing. In the colts the rate of grazing period was 87% on the first day and 98% on the second day. Kentucky blue grass was the most palatable for these horses.