Abstract: Four m e n and duodenum cannulated, Holstein lactating cows were used in a change-over design to determine the effects of NaOH, Formaldehyde or Urea treated barley on dsappearance of Dly Matter (DM), Crude Motein (CP), Amino Acids (AA), NDF, ADF, hemicelluloses and starch in m e n , Post Abomasal Tract (PAT) and total tract by mobile nylon bag techmque. Experimental treatments were coarse milled barley, barley treated with 3.5% NaOH, barley treated with 0.4% formaldehyde and barley treated with 3.5% urea that all chemical treated barley milled coarse before feeding. NaOH Treatment reduced concentratiom of Lysine and Cystine in the barley grain. All chemical treatments decreased m e n dsappearances of barley CP but only NaOH and Formaldehyde treatments also decrease total AA and some of the AA disappearances in the m e n . All chemical treatments increasedDM, OM, CP, starch, NDF, ADF and hemicellulose dsappearance of barley in the PAT. But only NaOH and Formaldehyde treatments increased total AA and most of AA disappearances inthe PAT. Effect of chemical treatments on increase of dsappearance of starch Met and Gly in the total tract was significant (p<0.05). Rumen dsappearance of TAA was lower than CP but PAT dsappearance of TAA was more than CP and finally total tract disappearance of TAA was more than CP. Individual AA in barley disappeared at different rates in the m e n and PAT. Consequently, the proportion of digesta CP and AA entering the intestine must be comidered. Key words: Barley grain, amino acids, mobile nylon bag, NaOH, formaldehyde, urea

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