Variation in feed intake of broiler chickens

With many broiler diets, particularly wheat–based diets, rate of passage of digesta limits intake and growth. In many trials, the relationship between feed intake and apparent metabolizable energy (AME) was negative or insignificant. In some trials, the limitation to voluntary intake was so severe that negative relationships existed between it and FCR. This is a consequence of the diversion of a large proportion of nutrients to maintenance rather than to growth. When feed intake is increased, a greater proportion of nutrients is used for growth and FCR is improved. Although intake was increased by supplementation with enzymes and by pelleting, variation between samples was not. Furthermore, rankings of various grains for feed intake and growth were affected by processing and enzymes. It is proposed that limitations to digesta passage rate are partly related to differences in the time required to hydrate the diet, a function of particle size and physicochemical properties.