Abstract IT IS useful to know how long it takes food to pass through the digestive tract. In order to maintain high productivity the hen must be constantly converting feed. The best converters of the feed nutrients are those individuals which digest their feed the best and empty the tract quickly so that additional feed can be consumed. The rate of passage of feed through the digestive tract has been expressed in various ways such as the time required to empty the crop, the lapse of time before the feed appears in the droppings and the time required to completely clear the digestive tract. There is considerable variation in the reported results concerning the rate of feed passage through the digestive tract of the hen. This no doubt is due to the fact that the rate is influenced by many factors, such as the amount of feed consumed, the mechanical condition . . .