Chemical composition and ruminal fermentation characteristics of selected forage species from traditional enclosure areas in the central highlands of Ethiopia

Abstract

This study aimed to characterize key forage species in terms of their chemical composition and ruminal fermentation characteristics thereby determining their nutritional value for ruminants. A total of 20 plots of 40 m x 40 m were established on pasture land in the highland and mid-highland agro-ecologies. Sixteen quadrats (0.5 m x 0.5 m) were randomly laid per plot and samples of 19 key forage species were collected at 50% flowering stages. Species identification was done on site by using guide books and a trained technician. The harvested pasture was sorted by species to allow the investigation between species variability in terms of nutrient contents and in vitro ruminal fermentation parameters. Forage species evaluated in the current study showed noticeable variation in nutritive values and ruminal fermentation parameters. Principal component (PC) analysis showed that the first three PC (PC1, PC2 and PC3) explained 84.2% of the total variation in the dataset. The key forage species clustered according to their chemical composition and in vitro fermentable parameters into five main groups. Centella asiatica forb (sole group) was superior in gas production at 24 h, fractional gas production rate (c) and effective gas production (EGP) but lower in neutral detergent fiber (NDF) and CH4 production. Forage legumes
were clustered close to each other and had higher crude protein (CP), ‘c’, and EGP production compared to forage grass. Forage grasses except Eragrostis tenuifolia were characterized by higher CH4 production compared to others. Therefore, appropriate management practices that maintain balanced proportions of herbs, forage legumes, and grasses may result in improved ruminal fermentation of the available diet while reducing methane emissions by ruminants fed on native pasture.