Acid Detergent Insoluble Protein as Tropical Forages Rumen Undegradable Protein Estimator

Abstract

The undegradable rumen protein fraction estimated from neutral detergent insoluble nitrogen (NDIN) was studied. A total of 540 samples were used, obtained from manual grazing simulation and esophageal extrusa in elephant grass and mombaça grass, from hays and from tropical grasses submitted to different fertilizing levels and cutting ages. The samples were analyzed for dry mater, lignin in sulfuric acid (LAS), lignin permanganate (LPER), neutral detergent insoluble protein (NDIP) and acid detergent insoluble protein (ADIP). The rumen undegradable nitrogenous fraction was done by incubating the samples for 240 hours in the rumen, followed by the treatment with neutral detergent, and finally the nitrogen in the residue was quantified to get undegradable protein insoluble in neutral detergent (UPIND). The results allowed to evidence no-equivalence and total absence of association, between predicted and observed values of the undegradable protein fraction. It is suggested that ADIP may not be used as an estimator of undegraded protein fraction. This fraction should be estimated by biological methods like the protocol adopted to get the concentrations of UPIND.