Prediction of Voluntary Intake, Apparent Digestibility and Digestible Dry-matter Intake of Hays by Sheep from Rumen Degradation Characteristics, Ruminal Outflow Rate and Rumen Fill

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  • めん羊における乾草の乾物摂取量,乾物消化率および可消化乾物摂取量の第一胃内分解性,流出速度および充満度からの推定
  • Prediction of Voluntary Intake Apparent

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Abstract

Nine hays with neutral-detergent fibre (NDF) and acid detergent fibre (ADF) concentrations ranging from 462 to 739 and from 319 to 447 gkg^<-1> dry matter (DM) respectively, were used to assess the possibility of predicting voluntary DM intake (DMI), apparent DM digestibility in vivo (DMD) and digestible DM intake (DDMI) by sheep from the rumen degradation characteristics represented as a rate and potential extent of degradation of the hays, outflow rate (k_1) from the rumen and rumen fill (Rf). Three sheep were used repeatedly for each hay in all the measurements. The degradation characteristics were measured by incubating samples in polyester bags in the rumen and the water soluble fraction (A) was measured. The exponential equation p=a+b(1-e^<-ct>) or p=A+B (1-e^<-ct>) was fitted to the results. Outflow rates (k_1) were determined by using Cr mordanted fibre prepared from each hay. Rf was given by the equation Rf=m/(c+k_1)+n/k_1(m=(a+6)/100, n=1-(a+6)/100). There were large differences in the DMI and DDMI measurements of hays varying from 40.4 to 84.8 and 21.4 to 50.3g day^<-1>kg^<-1>LW^<0.75> respectively, with wide variations in the degradation rate (c), solubility (A) and potential degradability (defined as a+b), k_1 and Rf. The Rf was highly correlated with the DMI (r=-0.928; P<0.01). The inclusion of K_1 or Rf with a, b and c or A, B and c in multiple regression to predict DMI, DMD and DDMI gave better results than when lag time for degradation (Lt) or NDF were used instead of k_1 or Rf. Consequently, the use of a, b, c and k_1 in a multiple regression equation gave the most precise prediction of DMI and DDMI having coefficients of determination R2 = 0.979 (residual s.d.=2.99g day^<-1> kg^<-1> LW^<0.75>) and 0.972 (residual s.d.=2.56g day^<-1> kg^<-1> LW^<0.75>), respectively. These results indicate that the accuracy of DMI and DDMI pre-dictions of hays may be improved distinctly by using k_1 or Rf with the rumen degradation characteristics.

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