Effects of Non-Fiber Carbohydrate on In vitro First Order Kinetic Disappearance of Neutral Detergent Fiber and Neutral Detergent Insoluble Nitrogen of Wheat Bran

摘要

An in vitro experiment was conducted to determine the effect of supplemental Non-Fiber Carbohydrate (NFC) on disappearance kinetics of Neutral Detergent Fiber (NDF) and Neutral Detergent Insoluble Nitrogen (NDIN) of Wheat Bran (WB) by mixed ruminal microorganisms. Non-supplemented or NFC supplemented WB (70 mg NFC g 1 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 disappearance of WB were measured. Data were analyzed as a complete randomized design using a 4? factorial arrangement. The 1st 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(t) = D(i).exp (-k2 time) + I; D(t) is potentially digestible residues; D(i) is potentially digestible fraction; k is fractional rate constant of disappearance (h-1) and I is indigestible fraction. In this experiment, Including of NFC in the fermentation medium had a significant (p<0.01) effect on the disappearance of NDF (0.48, 0.49, 0.45 and 0.46, respectively, for WB, WBSu, WBSt, WBSuSt) and NDIN (0.52, 0.58, 0.50 and 0.55, for WB, WBSu, WBSt, WBSuSt, respectively) of wheat bran. The fractional rate constant of NDF disappearance was greater (p<0.05) in both WBSt and WBSuSt samples compared with non-supplemented (0.06, 0.06, 0.12 and 0.12 h-1, for WB, WBSu, WBSt, WBSuSt, respectively). Also, indigestible fraction of NDF was greater (p<0.05) for 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 adding 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 disappearance. Indigestible fraction of NDIN was significantly increased when it was supplemented by starch or sucrose + starch (p<0.05).