DIETARY FORMULATION WITH COTTONSEED MEAL ON A TOTAL AMINO-ACID VERSUS A DIGESTIBLE AMINO-ACID BASIS

The results of previous experiments indicated that performance of chicks fed corn-cottonseed meal (CSM) diets was inferior to performance of chicks fed a corn-soybean meal (SBM) diet and that true digestibilities of amino acids (AA) in CSM were lower than those in SBM. Therefore, the current study evaluated the formulation of diets containing expander-solvent CSM on an equivalent total AA basis vs an equivalent digestible AA basis compared to a corn-SBM diet. True digestibility of AA in the CSM, corn, and SBM were determined using the precision-feeding assay with cecectomized roosters and TME(n) was determined using conventional roosters. One-week-old male chicks were then fed diets containing corn and SBM only or diets containing increasing levels of CSM from 5 to 40% that were formulated to be equal in total or digestible AA to the corn-SBM diet. All diets contained 20.7% CP and 3,200 kcal TME(n)/kg. Weight gain and feed efficiency of chicks fed 20% or more CSM on a total AA basis were less (P <.05) than those of chicks fed the corn-SBM diet. Growth performance of chicks fed up to 20% CSM on a digestible basis was equivalent to that of chicks fed the corn-SBM diet, but dietary levels of 30 or 40% CSM depressed performance even on a digestible basis. Increasing most essential AA by 15% in the 40% CSM (digestible basis) diet had no effect on performance. True digestible AA and ME values determined in chicks were similar to those determined in roosters. These results indicate that formulation of diets containing CSM on a digestible AA basis is superior to formulation on a total AA basis and that at least 20% CSM could be fed to chicks if the diet contains adequate levels of digestible AA and Fe to bind gossypol. The results also indicated that the depression in performance from feeding 30 or 40% CSM diets was not associated with dietary AA levels.