Faculty of Science and Agriculture

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Browsing Faculty of Science and Agriculture by Author "Beyene, S."

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    Species and spatio-temporal variation in the yield, nutritive value and in vitro ruminal fermentation characteristics of selected grass species from two communal grazing lands of the Eastern Cape.
    (University of Fort Hare, 2013) Kwaza, Ayanda; Beyene, S.
    Communal rangelands sustain a large proportion of the livestock in South Africa. A few dominant grass species contribute to the bulk of the livestock forage in these rangelands. Little is known on the chemical composition and in vitro ruminal fermentation characteristics of grass species grazed by ruminants in the communal grazing lands of Eastern Cape Province in South Africa. The objectives of this study were therefore to investigate seasonal and altitudinal variations in biomass yield, chemical composition, and in vitro ruminal degradability and cumulative gas production of selected (dominant) grass species. The grass species were collected over four seasons (summer, autumn, winter and spring) from three altitudes/landscape gradients (upland, gentle sloppy and bottomlands) across two communal areas (Hala in highland (Highveld) and Gqumashe in lowland (Lowveld)) of the Eastern Cape province, South Africa. In each altitude, three 50 m x 20 m plots, which served as replicates were marked to collect vegetation samples. A 5 x 4 x 3 factorial experiment in a randomised complete block design was used with season, altitude and grass species being the main factors, and with the plots within altitudes serving as blocks (replicates). Data analysis was done separately for the two communal study areas using the General Linear Models (GLM) procedure of SAS to test differences between species, seasons and altitudes. The common grass species in both grazing lands were Cynodon dactylon, Eragrostis chloromelus, Eragrostis plana, Sporobolus africanus and Themeda triandra. When the DM yield of all the grasses was combined, the results showed a generally low forage dry matter yield during the dry season. There was no significant (P>0.05) interaction between any of the main factors. Macro and micro mineral content of plant samples collected from the two communal grazing lands showed great variations (P<0.05) between species, seasons and altitude. In the Highveld, CP ranged from 3.9 to 6.5% DM being significantly highest (P<0.05) in Cynodon dactylon and lowest in E. plana. When all species were combined, higher CP was recorded for samples harvested in summer (5.5%) followed by spring and autumn, and lowest in winter (3.8%). In the Lowveld, Eragrostis chloromelus had higher (P<0.05) CP level followed by C. dactylon and T. Triandra. When all species were pooled, forage samples harvested in summer had a significantly higher (P<0.05) CP followed by spring, autumn and winter. In summary, CP content of all grasses was below the critical maintenance level for livestock especially during late dry seasons. In both areas, the highest NDF level was measured for Eragrostis plana and lowest for Themeda triandra. As for altitudinal differences, samples collected from the upland areas had generally the lowest (P<0.05) CP and highest ADF contents. For grasses harvested from the Highveld, C. dactylon produced the most (P<0.05) gas after 48 h of fermentation (794.6 ml/g DM) and also had the highest 48h DMD (415.1 g kg-1). Themeda triandra produced least (P<0.05) gas (742 ml/g DM) 48h post-incubation. The least (P<0.05) degradable species after 48 h was E. chloromelus (372.9 g kg-1). For grasses harvested from Lowveld, the 48h cumulative gas production was highest (822.7 ml/g DM) in E. plana and lowest (742.8 ml/g DM) in E. chloromelus, while S. africanus had least 48h DMD (327.9 kg-1). In both the Highveld and Lowveld, gas production and DMD were highest in the autumn season. It was concluded most grasses were deficient in calcium, magnesium, phosphorus and potassium. Therefore, it is recommended that mineral supplements should be offered to animals to improve animal productivity throughout the year. Findings of this study suggested that addition of protein and energy sources may be desirable in both grazing areas to meet the maintenance/production requirements of the grazing ruminants throughout the year.