Estimates on the Availability of Amino Acids in Soybean Oil Meal as Determined by Chick Growth Assay: Methodology as Applied to Lysine

Abstract

A crystalline amino acid diet, deficient in lysine but otherwise nutritionally adequate, was used in chick growth assays covering the period 9 to 14 days post hatching to estimate the availability of lysine in soybean oil meal (SBOM). Using regression analysis (weight gain vs. lysine consumed) and applying the slope-ratio technique, estimates of 80, 73, 77 and 74% were obtained when computed on the basis of total lysine consumed (A), when gain on test diets due to intake of crystalline lysine and SBOM-lysine was partitioned to reflect only gain attributable to SBOM-lysine (B), when partitioning was done by multiple regression (C), and when crystalline lysine was omitted from test diets (D), respectively. The conventional method of equalizing feed intake gave unrealistic values, but when feed was not restricted the estimate of availability was 74%. Autoclaving SBOM for either 2 or 3 hours lowered the estimate of availability from 73 to 54 and 44%, respectively (B).