Chemical components and enzyme and in vitro digestibility of woody shrubs used by ruminants in New Caledonian rangelands. II. Prediction equations of enzyme and in vitro digestibility of crude protein and organic matter

Abstract

In New Caledonia, as in many other countries, it is not realistic to consider in the short-term using all fodder assessment methods. Compare to herbaceous fodder, tropical shrubs nutritive value is not well known. Thus, prediction equations of some factors associated with the nutritive value of tropical shrubs and trees collected in New Caledonian extensive lands were computed in this study. On one hand, criteria were determined by enzyme methods: organic matter enzyme digestibility (SMO) and crude protein digestibility by pronase (MApro); on the other hand, by the in vitro method: in vitro digestibility of organic matter (dMOgt) and crude protein (MAgt) via the gas production method. This study shows the difficulty to provide prediction equations using chemical compound contents, which are commonly used for herbaceous species (MAT, NDF, ADF). Because of their usually high lignin content, their crude proteins partly bound to undigestible fibers and their tannin content, the use of chemical criteria such as ADL, MAadf and MAnadf (MAT bound or not to ADF) is necessary for fodder shrubs and trees. The accuracy of the equations is nevertheless reasonable for dMOgt and for the Fabacae family. On the other hand, equations based on MApro are not satisfactory except for Fabacae.