The objective of this study was to determine the metabolizable energy (ME) and amino acid digestibility of five soybean meal (SBM) samples using a precision-fed rooster assay and a chick assay. The experimental SBM samples evaluated were cold-pressed (extruded) soybean meals or solvent-extracted (defatted) soybean meal. Of the cold-pressed varieties (unheated), there was an ultra-low trypsin SBM, a low-trypsin SBM, and a heated and unheated commodity SBM. The solvent-extracted SBM was a heated commodity blend.
Semi-purified diets containing dextrose as the main energy source were formulated to meet the bird’s nutrient requirements, with each diet containing a different SBM product. The precision-fed rooster assay involved fasting five birds per diet for 24 hours; crop intubated with 35 grams of the test diet containing 46.58% cold-pressed or defatted SBM; and collecting excreta for 48 hours. The amino acid assay followed the same protocol, but cecectomized birds were used. For the chick assay, 480 one-day-old chicks were fed a standard corn-SBM starter diet for 17 days and then on day 18, the chicks were allowed ad libitum access to the SBM-dextrose diets. Excreta were collected on day 22, dried, ground, and analyzed for gross energy and crude protein and ME determined.
The SBM processed from soybeans genetically selected to have lower trypsin inhibitor levels and higher protein had higher ME values and increased amino acid digestibility compared to the commodity cold-pressed SBM samples. The researchers concluded that the genetic selection of soybeans for certain traits can have positive effects on the ME value and amino acid digestibility for roosters and chicks.