Tannin and in vitro digestibility of tropical browse: predictive equations

Abstract

Summative equations to predict digestibility of tropical browse species for cattle were tested by comparison to in vitro digestibility. Four equations were used for the comparison: first the 2 Van Soest equations, 1 using sulfuric acid lignin and the other using permanganate lignin, neither of which have a correction for tannins. And second, the 2 Horvath equations, each using 1 of the 2 above mentioned lignin values and both include a value for tannin content. The Van Soest equation using permanganate lignin and the Horvath equation using sulfuric acid lignin predicted the in vitro digestibilities of the leaf species quite well (r = 0.89 for both). The same Horvath equation predicted the digestibility of the high tannin species better than the Van Soest equation (r = 0.93 versus 0.84). For initial evaluation and ranking of browse species suitable for future research efforts, either equation suitable.