PREDICTION OF RUMEN UNDEGRADABLE AMINO-ACIDS THAT ARE DIGESTED POST-RUMINALLY

Data for in situ disappearance of DM, nitrogen (N) and amino acids in canola meal (CM) were used to determine degradation parameters require d to estimate effective degradabilities of these nutrients. The non-di gestible fraction of DM, N and amino acids in CM was determined using mobile bags after ruminal incubation for 12 h. Linear relationships we re determined between dependent variables, ruminal disappearance (DIS) or effective degradability (EDEG) of amino acids and independent vari ables, DIS or EDEG of DM or N. Use of EDEG vs. EDEG relationships, (r( 2) greater than 0.87 for amino acids other than methionine and cystine ) with the effective degradability of DM, as the independent variable, was the most effective approach over a wide range of rumen outflow ra tes (k) for prediction of amino acids that escaped ruminal degradation . Use of DIS vs. DIS (an estimate for EDEG of DM served as a value for the independent variable), or EDEG vs. DIS (disappearance of DM at in cubation time equal to k(-1) was the independent variable) relationshi ps was not as effective. Post-ruminal digestion was predicted as the d ifference between ruminal escape (based on estimates of effective degr adability) and that nutrient present in the residual DM in mobile bags recovered at the terminal ileum. Use of Linear EDEG vs. EDEG equation s, in association with a mobile bag technique, allowed for prediction of both ruminal escape and post-ruminal digestion of N and amino acids in CM over a range of outflow rates for feed particles from the rumen .