The objective of this trial was to investigate ruminal, intestinal and totaltract digestibility of acid detergent insoluble nitrogen (ADIN) in grazing cattle.Five Holstein x Zebu steers averaging 304 kg of body weight and 24 months ofage and fitted with esophageal, ruminal and abomasal cannulas were used in thisstudy. Animals were maintained in five 0.34-ha paddocks of Brachiaria decumbenswith or without concentrate supplementation. The experiment was conducted fromAugust to November of 2000 using four 21-days experimental periods. Evaluationof the forage ingested by the animals was done by collecting esophageal extrusasamples. The flow of fecal and abomasal dry matter was estimated by using bothinternal and external markers. Statistical analysis of ADIN digestibility wasconducted by adjustment of the linear regression equation with no interceptin the model and using ADIN inflow as independent variable and ADIN outflowas dependent variable. The deviation of the regression coefficient from theparametrical value 1.0 was considered to be digestible matter. Comparison betweenintake and abomasum and fecal flows of ADIN indicated that the observed totaltract digestibility (30.7%) of this nitrogen fraction occurred exclusively inthe intestine. Therefore, ADIN content of feeds can be considered only as anindicator but not as a predictor of nitrogen compounds potential digestibility.
