Chemical composition and in vitro ruminal fermentation of selected grasses in the semiarid savannas of Swaziland
Little is known about the grass species type, composition and nutritive value in the semiarid savannas that sustain most of Swaziland's cattle population through the seven-month-long dry season. This study was conducted to investigate the nutritional characteristics of grasses collected from two grazing areas (Big Bend and Simunye), which differed mainly in soil types. Mature grass species were harvested and evaluated for chemical composition (organic matter, neutral detergent fibre [NDF], acid detergent fibre [ADF], crude protein [CP] and minerals) and in vitro ruminal fermentation (in vitro gas production, in vitro organic matter degradability and partitioning factors). The most common grass species in the Big Bend grazing area were Bothriochloa insculpta, Cenchrus ciliaris and Urochloa mosambicensis. In the Simunye grazing area the most common species were B. insculpta, U. mosambicensis, Heteropogon contortus, Panicum deustum and P. maximum. For grasses harvested from Simunye, the most (P < 0.05) degradable (532 mg g−1 dry matter) was B. insculpta, which also had the least fibre (597 g kg−1 NDF and 351 g kg−1 ADF) and the highest CP content (79.8 g kg−1). The most common grass species harvested from the Big Bend area did not differ (P > 0.05) in their Mg, P, Cu, Fe, Zn, CP and NDF content. However, U. mosambicensis had the highest (P < 0.05) ADF content. The least fermentation efficiency (partitioning factor = 2.2 mg degradable organic matter [DOM] ml−1 gas) was observed for U. mosambicensis as a result of low DOM coupled with high cumulative gas production. It was concluded that all the grasses investigated in this study show a deficit for Ca, P and protein. Therefore, supplementation is needed to ensure maximum forage utilisation and to satisfy nutrient requirements of ruminant livestock.
Available from: Solomon Beyene
- "On their study around watering points, Fensham, Holman & Cox (1999) and Beukes & Ellis (2003) also concluded that there is a general trend for reduced forage biomass with increasing distance from water points. Both DM yield and estimated G.C reported in this study were extremely low compared with the study of Tefera et al. (2009) in Swaziland, but similar to the report of Abule, Snyman & Smit (2007) in Ethiopian semi-arid rangelands. Based on an inference from the long-term average rainfall of the study area (500 mm), which was also recorded during the study period, the mean DM yield, and hence G.C was extremely too low to carry the potential number of animals that this area should support. "
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ABSTRACT: This study examined rangeland condition and degradation characteristics of the semi-arid savannahs of Swaziland in response to distance from dip-tank points in three soil types. Eight dip-tanks, three each in sandy and loamy, and two in stony soils, were selected. Two transects (1 km) radiating from each dip-tank were established. Total herbaceous yield (range: 176-363.8 kg DM ha(-1)) and grazing capacity (47.5-111.5 ha LSU-1) were very low throughout the studied areas. Palatability and ecological values of grasses were 18.7-67.6% and 43.2-64.1%, respectively. Most sites were dominated by woody seedlings and saplings (<0-2 m). Most vegetation variables did not respond considerably to distance, soil types and sites within soil types. When all measured variables were combined, the results showed a generally poor range condition scores across distance points from the dip-tank. A holistic restoration programme with full involvement of communal farmers, experts, policy makers and extension workers is recommended.
Available from: Patrick Duncan
- "However, our short-term study indicates that grazing seems not to be an exceptional event. During our observations, the grass layer was already senescent, indicating very low digestible protein/ energy content (Tefera et al., 2009; Safari et al., 2011). "
Available from: Victor Mlambo
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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 thatmost 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.
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