BOTANICAL AND CHEMICAL COMPOSITION OF COMMON GRASS SPECIES AROUND DIP–TANK AREAS IN SEMI–ARID COMMUNAL RANGELANDS OF SWAZILAND

Abstract

Communal rangelands in arid and semi–arid areas of southern Africa are the source of virtually all feeds for wild and domestic ruminants. However, the quality and quantity of feed fluctuates in response to rainfall patterns. Little is known about the capacity of these rangelands to support ruminant productivity during the 4-month dry season. This study was therefore designed to assess the botanical composition of grasses and determine nutritive values of selected grass species growing in the communal rangelands of Swaziland at the start of the dry season. Vegetation survey and sampling were carried out in two semi–arid ecological zones (Lower Middleveld (LMV) and Lowveld (LV) savannas). Dry matter (DM), organic matter (OM), crude protein (CP), minerals, neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents were determined. Of the 20 grass species identified in the two zones, 9 were perennials and 11 were annuals. Only 3 the grass species were classified as highly palatable. Grass species showed significant (P<0.05) (LMV) and non–significant (LV) variations in the DM yield. In both ecological zones the highest NDF level was measured in Panicum maximum and Urochloa mosambicensis and lowest in Digitaria longiflora and Eleusine coracana. In the LV region, P. maximum ranked first in CP content, while E. coracana ranked last. In the LMV region, the level of CP was highest in P. maximum, and lowest in D. argyrograpta. In most instances, macro and trace elements showed variations (P<0.05) between grass species. Grass species collected from the two ecological zones showed great variations in NDF, ADF, CP, macro and microminerals. P<0.05– It was concluded that most grasses were deficient in protein, phosphorus and potassium. It is recommended that protein and mineral supplements should be offered to animals to optimize the utilization of grasses and improve animal productivity during the dry season.