Fibre Analyses of an Evergreen, a Deciduous Woody and a Non-woody Dicotyledon: Comparison of Two Techniques

Forage fibre content is frequently used as an index of forage quality, where high fibre content indicates low forage quality. Although the acid-detergent fibre (ADF) and acid-pepsin digestibility (AP) techniques have provided similar estimates of forage quality for a variety of herbaceous monocotyledonous plants, these techniques have provided dissimilar estimates of fibre content for a willow, a deciduous woody dicotyledonous forage. This lack of correlation has been attributed to variations in the proportions of stem and leaf material that comprised the willow samples. Both the ADF and AP techniques were used to compare the estimates of the fibre content of willow leaves, willow sterns, an evergreen ericaceous dwarf shrub. and a non-woody dicot. A strong negative correlation and a linear relationship were found between the fibre content, as determined by ADF, and the digestibility, as determined by AP, for each sample type. The linear relationships were significantly different for all sample types. This suggests that, although phenological changes in fibre content may differ between samples, the two techniques provide a very similar estimate of forage quality in dicotyledonous forages. In the case of deciduous woody dicotyledons, leaf and stem material must be separated prior to the analyses.