Landscape and Seasonal Effects on Crude Protein, Fibre and In Vitro Fermentation Characteristics of Common Grass Species in Semi-arid Communal Grazing Lands of South Africa

This study investigated the influence of season and landscape on the nutritive value of common grass species growing in two (Highland and Lowland) communal rangelands of the Eastern Cape Province, South Africa. Grass samples were harvested from three landscape gradients (upland, sloping and bottomland) over four seasons (summer, autumn, winter and spring) for crude protein (CP) and fibre contents determination, and over two seasons (autumn and winter) for in vitro ruminal fermentation analysis. In the Highland, Cynodon dactylon had significantly the highest CP content (6.5%), while Eragrostis plana (3.9%) and Sporobolus africanus (4.0%) had the least. Grasses harvested in the winter season had the least CP, while those harvested in autumn and summer had the highest. In the Lowland, CP content in winterharvested grass ranged from 2.7% (S. africanus)-4.8% (C. dactylon). Of the three main factors, only season had a significant effect on in vitro ruminal fermentation parameters in both study areas. Ruminal degradability was lower in winter-harvested compared to autumn-harvested grasses. It was concluded that generally seasonal variation imposed greater influence on nutritive value of grass herbage than spatial variation. Crude protein content of grass herbage in both communal grazing areas was likely to be inadequate for maintenance of ruminant animals, but the severity depends mainly on season. This urges the need for protein supplementation in order to improve animal productivity.