Skip to content
Search Library
thumbnail

Horses, like humans, are basically diurnal, or awake and active during the day. At night, biological processes help members of both species repair tissues as they move less and rest more. Various genes in muscle and other tissues are involved in other 24-hour cycles that are coordinated with hours of sunlight and darkness. These cycles determine many aspects of an individual’s physiology, metabolism, and behavior.

In a study designed to evaluate the influence of exercise on equine circadian rhythms, researchers at University College-Dublin used six healthy Thoroughbred mares that had been pastured for a year and were not in a structured exercise program. Muscle biopsies for each horse were taken every four hours at the beginning of the study, and after eight weeks of a program in which the horses exercised for a 20-minute period at mid-morning of each day.

Genes related to muscle metabolism were compared from samples taken at both times. In the pre-exercise biopsies, these genes, which were known to be important in performance horses, were expressed constantly during a 24-hour period. In samples taken after eight weeks of exercise, genes involved in muscle regeneration and repair were not turned on at night, Instead, genes that help in protecting muscles from stress were turned on just before the time of day when the exercise had been occurring. Thus, the biological rhythms had shifted in response to the horses’ exercise schedule such that optimal performance could be carried out at an anticipated time of demand.

The researchers said that this effect would be most obvious in horses that performed short periods of intense exercise, whereas horses that performed longer periods of less intense work such as endurance racing would probably not show as extreme a shift in biological rhythms due to exercise schedules.

X

Subscribe to Equinews and get the latest equine nutrition and health news delivered to your inbox. Sign up for free now!