Relationship between Two Different-Type Equations Analyzing Increase in Dry Matter Indigestibility with Growth of Forages

This study was planned to relate two different-type equations analyzing the increase in dry matter indigestibility (IDMI) in the growth of forages. The following equation showed the relationship between two equations, namely, the the left-hand side equation by Masuda (1985) and the right-hand side equation which was a changed form of the original equation by Shimojo et al. (1995). I₁/W₁ · [exp {(RGR_i - RGR_w) · (t₂ - t₁)} - 1] = (1 - W₁/W₂) · (SFR/RGR_w · D/W - I₁/W₁), where W = forage dry weight (W₁ ≠ W₂), I = dry weight of indigestible materials, D = dry weight of digestible materials (D₁ ≠ D₂), RGR_w = mean relative growth rate of forage, RGR_i = mean relative growth rate of I, (1 - W₁/W₂) = forage growth index [FG index], SFR = mean specific formation rate of I per unit D, D/W = the ratio of D to W [D ratio], {(SFR/RGR_w) · (D/W) -I₁/W₁} = a changed form of DMP index (DMP index: index for dry matter partition into I). The following results were obtained: RGR_i was found to be related to SFR from their positions in the equation, and this might support the suggestion by Masuda (1985) about the close relation of RGR_i to SFR. SFR might substantially relate the equation by Masuda (1985) and the equation by Shimojo et al. (1995). It was suggested that there was a close relationship between two different-type equations analyzing the increase in dry matter indigestibility with growth of forages.