THE USE OF ACID DETERGENT-INSOLUBLE NITROGEN TO PREDICT DIGESTIBILITYOF RUMEN UNDEGRADABLE PROTEIN OF HEAT-PROCESSED PLANT-PROTEINS

The usefulness of acid detergent insoluble nitrogen (ADIN) to predict digestibility of rumen undegradable protein (UDP-D) of heat processed and unprocessed plant proteins was investigated. A series of drum roas ted protein sources, sunflower, cottonseed and soybean oilcake meals, in addition to whole soybeans, whole sunflowerseed, whole cottonseed a nd whole lupinseed, were evaluated in this study to test the relations hip between ADIN (% of total N) and UDP-D. Using ADIN as a screening p arameter, five samples on average of each protein source together with the unprocessed control were selected for an in situ study using the mobile bag technique (MET) to determine UDP-D. Digestibility of undegr adable protein was not significantly decreased as a result of heat tre atment, when ADIN values were below 12-15%, but progressively decrease d when ADIN was higher, suggesting substantial heat damage. Ruminal ni trogen digestibility also decreased (p <0.05) with heat treatment. Dig estibility of undegradable protein was predicted with a r(2) = 0.72 an d error of estimate (Sy.x) of 4.78%. The prediction equation (p <0.001 ) of UDP-D (%) = 91.9 - 0.025 (ADIN, % in DM)(2), could therefore be a satisfactory guideline for predicting UDP-D and heat damage of the ab ove-mentioned heat processed and unprocessed plant protein sources.