Effect of non-fiber carbohydrates on in vitro first order kinetics disappearance of cellulose

ABSTRACT

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 11 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