The The chemical composition and in vitro dry matter digestibility of herbaceous forage legumes adapted to arid Namibia

Abstract

The nutritional quality of herbaceous forage legumes adapted to the arid environment of Namibia has not been characterised. These legumes are important protein feed resources for animals. The study was conducted to determine the chemical composition and in vitro digestibility of four herbaceous legumes, namely Tylosema esculentum, Vigna unguiculata, Lablab purpureus, and Mucuna pruriens. The legumes were harvested at the vegetative growth stage and separated into leaves, stems, and whole plant fractions. The Tylosema had the lowest DM content in the leaf, stem, and whole plant fractions compared to other legumes, which also differed significantly. The ash content of the Vigna leaf and whole plant fractions was higher, 16.93% and 26.32%, respectively, while Lablab had a high ash content in the stem fraction, 10.40%. Tylosema had the lowest ash content among legumes in all fractions, ranging from 4.81% to 7.87%. Tylosema had the highest OM values, ranging from 92.13% to 94.20%. Lablab had the highest CP in all plant fractions, ranging from 12.95% to 30.05%. The legumes had similar hemicellulose content in leaf and whole plant fractions, while the stem fraction of Vigna had the highest hemicellulose content. The legumes had significantly different in vitro DM digestibility. Vigna recorded the highest DM digestibility in the leaf (88.83%) and stem (74.93%) fractions, while Lablab recorded the highest digestibility in the whole fraction (84.53%). In conclusion, forage legumes differed in chemical composition and in vitro DM digestibility, but all had adequate protein above the minimum requirement of 7% for ruminant livestock diets.