Abstract
Few papers have been published on the changes of glucose, pyruvate, and lactate in blood in horses. In the meanwhile, these substances have been regarded as good indices of muscular activity in human beings and other animals . Then, observation was made on horses to clarify diurnal rhythm at rest and changing rate of these substances during exercise. The results obtained are as follows. 1. In diurnal rhythm, both glucose and pyruvate increased after morning feeding, and both pyruvate and lactate increased at midnight . In any case, these substances increased by about 40-60% at rest in horses. 2. Experiments of exercise were performed by two quite different running methods. One method was running for a relatively short distance at high speed and the other, running for a long distance at low speed . Lactate increased in both experiments, but the increase was not so remarkable at low speed as at high speed. On the other hand, there was no increase in pyruvate but after cantering. Also, glucose decreased in both experiments, although the rate of its decrease was high in the running for a long distance . 3. Then, it would be considered that the change of lactate only is superior to that of L/P ratio as an index of intensity of muscular activity in horses, taking the sampling condition into consideration, and glucose is more effective as index of ability than as index of intensity of exercise, since it exerts infuence upon the sensitivity to both in-and output and the volume of con sumption during exercise.
