Comparative Feed Ingredient Composition

An important study to evaluate the apparent ideal digestibility of amino acids of various feed ingredients was conducted by Dr. Ravindran at the University of Queensland in Gatton, Australia. The research team determined apparent ideal digestibility coefficients for a number of cereal grains, cereal by-products, plant protein sources and animal protein sources in a series of digestibility assays. Four thirty-five day old birds per pen were fed ad libitum the assay diets from day 35 to 42 of age. The assay involved feeding three pens per test ingredient. To test the amino acid digestibility assay, a sample of soybean meal was included in seven assays as a reference ingredient. The coefficient of variation for the digestibility of amino acids in the reference soybean meal across all assays was less than 0.04 percent indicating that the assay-to-assay variation was small. There were no significant differences in the crude protein and/or amino acid digestibility coefficients for the seven soybean meal samples.

In the oilseed meals assayed, soybean meal and sunflower meal had the highest amino acid digestibilities, followed by canola meal and cottonseed meal. The overall average amino acid digestibility coefficient (average and range of values for all samples) was: soybean meal 82%, (75-88%); sunflower meal 82%, (73-92%); canola meal 78% (69-86%); and cottonseed 71% (61-86%). The researchers reported that the relative amino acid digestibility rankings for the various oilseed meals determined in this study with growing chickens are in general agreement with studies with older birds and growing pigs. The high relative amino acid digestibility of the soybean meal samples compared to other feed ingredients provide insight into why soybean meal is used in feed formulations where minimal amino acid levels are critical for top animal and bird performance.

Composition of various feed ingredients

(*) Average digestibility of all amino acids and standard deviations

Ravindran, V. and co-workers. 2005. Apparent ideal digestibility of amino acids in dietary ingredients for broiler chickens. Animal Science 81: 85-97.