1Graduated from Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
2Department of Animal Sciences, Excellence Center for Animal Sciences, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
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.