A broiler chick bioassay for measuring the feeding value of wheat and barley in complete diets

Energy is an important component of poultry feed and is derived principally from cereal grains. Unfortunately, all of the chemical energy is not available to the bird, and biological assays must be used to determine the digestible energy value of a cereal grain. The bioassay described uses four pens of six male broiler chicks, complete diets containing 80% of a test cereal grain (with or without an appropriate commercial enzyme), and ad libitum feed intake. Apparent metabolizable energy values (kilocalories per kilogram of cereal grain, DM basis) values are calculated from gross energy and acid insoluble ash measurements of diet and excreta collected for 24 h at 16 d of age. To monitor variation between broiler chick assays, due to bird, environment, etc., common control samples of Hard Red Spring (HRS) and Canadian Prairie Spring (CPS) wheat were tested in each of 15 separate assays over 2 yr. Similarly, for barley, control samples of hulled and hulless barley were repeatedly tested in five assays. Broiler performance in this study was lower than expected for commercial broilers, in part due to a high dietary cereal grain component and the fine mash texture. However, AME values as determined were comparable to those reported in the literature for wheat and barley. The CV for AME measured among pens, representing the intra-assay CV, was between 1.2 and 3.4% and was lower with enzyme supplementation. The interassay CV was only slightly higher than the intra-assay CV. This assay provides precise estimations of ME in cereal grains fed to young broilers that can be used for diet formulation or for verification of laboratory measures of feeding value of cereal grains.