Comparison of several in vivo digestibility procedures to determine lysine digestibility in poultry diets containing heat treated meat and bone meals

1. Three subsamples of a batch of meat and bone meal (MBM0) were heated at 150 degrees C for 1.5 h (MBM1.5), 3 h (MBM3) or 5 h (MBM5). 2. The MBM's were included in 4 wheat-gluten based diets, each limiting in lysine. 3. The lysine digestibility for each of the diets was determined using precision-fed intact adult cockerels and caecectomised adult cockerels, ileal cannulated adult cockerels, the ileal digesta and excreta of young growing chickens. 4. The results of the digestibility assays were compared with the relative amount of lysine available as determined by growth assay. 5. Comparison of the regression lines of digestible lysine (determined with the digestibility assays) on available lysine (determined by growth assay) indicated that while the magnitude of the digestibility values varied significantly (P less than 0.05) depending on the type of assay used, the differences in lysine digestibility as a result of heat treatment across the 4 diets was the same when comparing assays (the regression lines were parallel). 6. The results of each digestibility assay also correlated with relative digestibility values determined by growth.