An in vitro experiment was conducted to determine the effect of supplemental Non-Fiber Carbohydrate (NFC) on dsappearance kinetics of Neutral Detergent Fiber (NDF) and Neutral Detergent Imoluble Nitrogen @IDIN) of Wheat Bran (WB) by mixed nuninal microorganisms. Non-supplemented or NFC supplemented WB (70 mg NFC g- DM of WB as Sucrose (WBSu) or Starch (WBSt) or a 1 : 1 mixture of Sucrose + Starch (WBSuSt)) were incubated in bottles containing rumen fluid medium. The samples were incubated for 4,8,16 and 48 h at 39°C. After each incubation time, NDF and NDIN dsappemce of WB were measured. Data were analyzed as a complete randomized design using a 4x4 factorial arrangement. The 1 st factor consisted of supplemental NFC type and the 2nd factor consisted of incubation time. Kinetic disappearance rate of all samples was determined using first order exponential model of D, = D,,.exp (-k2 time) +I; D,, is potentially digestible residues; D,, is potentially dgestible fraction; k is fractional rate constant of disappearance (h-\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\') and I is indgestible fraction. In this experiment, Includng of NFC in the fermentation medium had a significant (p<0.01) effect on the dsappearance of NDF (0.48, 0.49, 0.45 and 0.46, respectively, for WB, WBSu, WBSt, WBSuSt) andNDIN (052,058,050 and 0.55, f o r m , WBSu, WBSf WBSuSf respectively) of wheat bran. The fractional rate comtant of NDF dsappearance was greater (p<0.05) in both WBSt and WBSuSt samples compared withnon-supplemented (0.06, 0.06, 0.12 and 0.12 h-I, for WB, WBSu, WBSf WBSuSf respectively). Also.. indi-ge stible fraction of NDF was -gr eater (,~. K0.05f)o r treatments receiving- starch or sucrose + starch as the source of supplemental NFC when compared with non-supplemented WB. However, when sucrose was added, the indigestible fraction of WB was similar with the non-supplemented sample. The fractional rate of NDIN disappearance in WB exhibited (p<0.05) an increase in response to addng the sucrose + starch supplement when compared with the non-supplemented WB and it was decreased when starch was added. Including of sucrose in the medium had no significant effect on fractional rate of NDIN dsappearance. Indigestible fraction of NDIN was significantly increased when it was supplemented by starch or sucrose + starch (p<0.05).

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