Order of amino acid limitation in meat and bone meal

Three experiments were conducted to determine the order of amino acid (AA) limitation in meat and bone meal (MBM) using AA addition and deletion assays. In two addition assays, various individual and combined additions of eight AA were made to semipurified basal diets containing 16% protein solely from a MBM. The two MBM had previously been determined to vary greatly in protein quality. In the deletion assay, a semipurified basal diet containing 13.5% CP provided solely by MBM was supplemented with L-Thr, L-Val, DL-Met, L-Leu, L-Ile, L-Phe, L-Tyr, L-Lys-HCl, L-His, and L-Trp to fulfill the Illinois Ideal Protein or AA pattern on a digestible basis. Each AA was then deleted individually from the basal diet, and the effect of its deletion on growth performance was assessed. In both addition assays, supplementation of the MBM basal diet with Trp and Cys together yielded a large increase in growth performance, whereas supplementation with these AA individually had no effect. These results indicated that Trp and sulfur AA (with a primary need for Cys) were equally first limiting in the MBM. The order of limitation for the other AA was unclear. The results of the deletion assay showed that deletion of Trp, Thr, Phe + Tyr, Ile, Met, Lys, Val, or His significantly depressed growth performance. The results of the combined addition and deletion experiments indicated that the order of AA limitation in MBM was 1) Trp and sulfur AA, 2) Thr, 3) Ile and Phe + Tyr, 4) Met, 5) Lys, and 6) Val and His. The deletion assay using diets formulated on an ideal protein basis was more effective than the addition assay for determining the order of AA limitation in MBM.