Chemical composition and in vitro ruminal fermentation of selected grasses in the semiarid savannas of Swaziland
ABSTRACT 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.
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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.African Journal of Ecology 07/2014; 52(4). DOI:10.1111/aje.12155 · 1.00 Impact Factor
African Journal of Ecology 08/2012; 50(2):247-250. DOI:10.1111/j.1365-2028.2011.01314.x · 1.00 Impact Factor
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ABSTRACT: The application of n-alkane as markers to estimate herbage intake, apparent digestibility and species composition of diet consumed by grazing sheep was studied. Six local Mongolian sheep were used to determine dry matter (DM) intake, apparent DM digestibility and species composition of diet during summer, autumn and winter. Animals were orally dosed twice daily with n-alkane gelatin capsules containing 60 mg C32-alkane as an external marker. Diet composition was estimated by comparing the odd-chain n-alkanes pattern profile (C27-C31) of the consumed plant species with the n-alkanes fecal concentrations of grazing animals, using a non-negative least squares algorithm called EATWHAT software package. The alkane pair C32:C33 and C33 alkane were used to estimate DM intake and diet apparent DM digestibility, respectively. The results showed that daily dry matter intake of the sheep were 1.77, 1.61 and 1.18 kg d−1 in summer, autumn and winter, respectively. Apparent DM digestibility, crude protein (CP), metabolizable energy (ME) and neutral detergent fiber (NDF) intake of diet consumed by sheep decreased significantly (P<0.01) from summer to winter, with no evident changes in ADF and ADL intake. Diet composition indicated Artemisia frigida Willd was the most dominant diet component, contributed 79.68, 68.12 and 86.26% of sheep's diets in summer, autumn and winter, respectively. Cleistogenes songorica Ohwi and Convolvulus ammannii Desr were the important components of the diet. Although Stipa breviflora Griseb is one of the main plant species in the study area, the sheep rarely choosed it. The study indicated that CP and ME in diet consumed by sheep were deficient in winter. Therefore, appropriate supplementation strategies should be indispensable during this period.Journal of Integrative Agriculture 05/2014; 13(5):1065–1072. DOI:10.1016/S2095-3119(13)60502-X · 0.63 Impact Factor