An in vitro experiment was conducted to determine the effect of supplemental non-fiber carbohydrate (NFC) on the disappearance kinetics of cellulose (Ce) by mixed ruminal microorganisms. Non-supplemented or NFC supplemented cellulose (467 mg NFC/g cellulose as sucrose (CeSu) or starch (CeSt) or a 1:1 mixture of sucrose + starch (CeSuSt)) were incubated for 24, 48, and 96 h at 39°C. After each incubation time, pH, ammonia-N concentration and cellulose disappearance were measured. The disappearance kinetics rate of all samples was determined using first order exponential model of D(t) = D(i).exp (-k. time) + I; where D(t) is potentially digestible fraction; D(i) is potentially digestible residues; k is digestion rate of cellulose (h-1) and I is indigestible fraction. In this experiment, inclusion of NFC to the rumen fluid medium resulted in a significant depression (P<0.01) in the extent of cellulose disappearance. The disappearance rate constant of cellulose was significantly higher (P<0.05) in non-supplemented samples as compared with those treatments containing NFC. The indigestible fraction of cellulose was significantly higher (P<0.05) for treatments containing sucrose or sucrose + starch as the source of supplemental NFC as compared with nonsupplemented cellulose. However, when starch was added, the indigestible fraction of cellulose was similar to those of non-supplemented samples. The inclusion of NFC resulted in a significant reduction (P<0.01) in pH of the medium, but had no significant effect (P>0.05) on ammonia-N concentration.

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