Formation of indigestible materials from digestible materials and photosynthates in the growth of Rhodes grass (Chloris gayana Kunth)

This study was conducted to analyze the formation of indigestible materials from digestible materials and new photosynthates in the growth of Rhodes glass, using the following equation. 1/W - dI/dt = D+dW/dt/W - (1/D+dW/dt - dL/dt) - dI/dL, where W = forage dry weight (W-1 not equal W-2), I = dry weight of indigestible materials, L = amount of lignin, D = dry weight of digestible materials (D-1 not equal D-2), dW/dt = new photosynthates, (D + dW/dt) = amount of source materials [S] for I formation, (1/W).(dI/dt) = formation rate of I [FRI], (D + dW/dt)/W = the ratio of S to W [S ratio], {1/(D + dW/dt)}.(dL/dt) = lignification rate of S [LRS], dI/dL = formation of I per unit increase in L [FIL]. This equation was applied to samples from Rhodes grass (Rg) cut at 25, 41 and 74 days of regrowth. Each attribute in the equation was given a bar on it to show mean value over the Ist interval of 16 days and over the 2nd interval of 33 days, respectively. The following results were obtained: Higher (FRI) over bar in the 1st interval than in the 2nd interval was mainly due to higher (LRS) over bar in the Ist interval with some contribution by higher <(S ratio)over bar>. This suggested that lignification of source materials composed of digestible materials and new photosynthates was the main factor promoting the formation of indigestible materials in the comparison between the 1st and 2nd intervals. It was suggested that the new equation presented in this study gave a macro analysis of the formation of indigestible materials from digestible materials and new photosynthates with growth of tropical grasses.