Formation of Indigestible Materials and Increase in Dry Matter Indigestibility in the Growth of Two Tropical Forages

This study was conducted to analyze the formation of indigestible materials [equation (A)] and the increase in dry matter indigestibility [equation (B)] in the growth of Rhodes grass (Rg) and Greenleaf desmodium (Gd). 1/W · dI/dt = C/W · (1/C · dL/dt) · dI/dL, where (1/W) • (dI/dt) = formation rate of I (indigestible materials) per unit W (forage dry weight) [FRI], C/W = the ratio of C (cell wall constituents) to W [CWC ratio], (1/C) • (dL/dt) = formation rate of L (lignin) per unit C [Specific FRL], dI/dL = formation of I per unit increase in L [FIL]. I₂/W₂ - I₁/W₁ = (1 - W₁/W₂) · (FRI/RGR_w - I₁/W₁), where (I₂ /W₂- I₁ /W₁) = increases in dry matter indigestibility [IDMI], W₁ ≠ W₂, (1- W₁/ W₂) = forage growth index [FG index], RGR_w = mean relative growth rate of forage, (FRI/RGR_w - I₁ /W₁) = index for dry matter partition into indigestible materials [DMP index]. Each attribute was given a bar on it to show mean value over the interval t₁ to t₂. The results obtained were as follows. 1. FRI was higher in Rg than in Gd and this was due to both higher CWC ratio and higher FIL in Rg. 2. IDMI was larger in Rg compared to Gd, which was due to higher DMP index with some contribution by FG index. It was suggested that this method was available for a macro analysis of the change in dry matter indigestibility occurring in the growth of forages.