Chemical and physical parameters of forage legume species introduced in the Capricorn region of Limpopo Province, South Africa

Author: H.K. Mokoboki, L.R. Ndlovu and K.K. Ayisi
Year: 2002
Issue: 4
Volume: 32
Page: 247 - 255

The purpose of the study was to evaluate the nutritive value of the forage legume species, Centrosema pascuorum, Lablab purpureus, Macroptilium bracteatum, Macroptilium gracile and Vigna oblongifolia as feed for ruminants in the Capricorn region of Limpopo Province, South Africa. It was hypothesized that forage legumes grown in the Province will be high in fibre and polyphenolics because of the high temperatures and low rainfall in the region. The experimental field was divided into four replications with the five different legume species within each replication, using a randomized complete block design. The plots were hand-harvested 16 weeks after planting, the material sampled, air-dried in the laboratory and analysed for physical parameters, chemical composition and in vitro enzymatic degradability. Lablab purpureus had the highest dry matter (DM) yield of 8 tons/ha followed by C. pascuorum with 2 tons/ha, whilst the other three species had a similar DM yield of approximately 1 ton/ha each. Physical characteristics varied from 2.88 to 4.45 ml/g for packed volume and 6.79 to 9.42 g/g for water retention. The crude protein composition varied from 236.8 to 259.6 g/kg DM, neutral detergent fibre from 418.3 to 505.8 g/kg DM, acid detergent fibre from 335.0 to 374.6 g/kg DM, the DM ruminal degradability from 611.1 to 712.9 g/kg DM and the organic matter (OM) degradability from 586.4 to 688.7 g/kg DM. The concentrations of total phenolics and extracted condensed tannins varied from 19.35 to 48.37 g/kg DM and from 17.7 to 33.5 g/kg DM, respectively. It was concluded that the biotic environment in the Limpopo Province did not impact negatively on the potential nutritive value of these forage legumes since the concentrations of fibre and phenolics were below levels expected to have detrimental effects on animals, and the ruminal degradability of their DM and OM was high.

Keywords: Forage, legume, Nutritive value, physical parameters, Tannins
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