The energy value of cereal grains, particularly wheat and sorghum, for poultry

Abstract

Results from the Premium Grains for Livestock Program were analysed to identify variation in the energy value for laying hens and broiler chickens of cereal grains including wheat, barley, oats, triticale, sorghum and rice. There was wide variation in apparent metabolisable energy (AME) within and between grain species for both layers and broilers. While the range in AME values was similar for most grains in layers and broilers, there were varying responses to specific samples. AME values tended to be higher in layers than broilers for barley, frosted triticale and naked oat samples. More AME was obtained from rice by broilers. There was little relationship between AME content of grains and the amount eaten by layers or broilers. When wheat and sorghum, the most common grains used by the Australian poultry industry, were compared, AME was considerably higher for sorghum in both layers and broilers. The intake of sorghum based diets was also higher for layers, but not for broilers. Layers offered sorghum based diets consumed 13% more AME daily than those offered wheat based diets. However, for broilers, daily intake of AME was similar for sorghum and wheat based diets. Despite a similar daily intake of AME, broilers offered wheat based diets grew 20% faster and used 13% less feed than those offered sorghum based diets. The poor utilisation of energy from sorghum based diets was attributed to a low availability of amino acids, with arginine as possible first limiting amino acid, due to the low content and digestibility of sorghum proteins. In addition, asynchrony in the timing of absorption of amino acids from casein, the main protein source in the experimental diets, and glucose from the delayed digestion of starch granules surrounded by a relatively indigestible protein matrix is thought to have contributed to the lower utilisation of energy from sorghum than from wheat based diets.