The relevance of drowsiness in the circadian cycle of farm animals

Electrocorticography and concurrent electromyography were used to establish the quantitative duration of the states of sleep and wakefulness during the circadian cycle, and also during the night-time, in four species of farm animals. Associated attitudes and physiological data were also recorded. Drowsiness is described as a definite stable state of wakefulness, as opposed to alert wakefulness. The state of wakefulness occupied 85 per cent of the 24-hr period in the herbivorous species studied but only 67 per cent in pigs. Cows spend the greater proportion of this wakeful period in the state of drowsiness, horses spend the greater proportion in alert wakefulness. A considerable amount of the wakeful period of farm animals well-accustomed to their environment is spent in the drowsy state, when they are not asleep or actively ingesting or searching for food.