Addition of ruminal escape methionine and lysine to meat and bone meal

A growth study was conducted to determine the effects of adding ruminal escape methionine and lysine to meat and bone meal (MBM). A basal diet of 44% sorghum silage, 44% corncobs, and 12% supplement (DM basis) was individually fed to 60 crossbred steers (234 +/- 14 kg). Supplements contained either urea, MBM, MBM plus protected methionine (MBM + M), or MBM plus protected methionine and lysine. Protein sources were fed to supply 30, 40, 50, and 60% of the supplemental CP, with urea supplying the remainder. Protein efficiency, calculated as gain above the urea control vs natural protein intake using the slope ratio technique, was used to evaluate the protein sources. The most efficiently used protein source was MBM + M, which was greater than MBM alone (P < .10). Meat and bone meal plus protected methionine and lysine had a protein efficiency similar to MBM + M (P > .30), indicating that lysine was not limiting. True protein digestibility of MBM in the gastrointestinal tract of lambs was determined to be 86.1%. In situ analysis performed by 12-h ruminal incubation of MBM determined the escape CP to be 53.0% of CP. Amino acid analysis was conducted to compare supplies to requirements for live animal gain. The urea control failed to meet the metabolizable protein requirement. Feeding MBM to provide additional metabolizable protein failed to provide an adequate amount of the essential amino acid methionine, which was first-limiting. These data indicate that protein efficiency of MBM can be enhanced by the addition of ruminal escape methionine.