This study was undertaken to determine the degradation characteristics and in vitro gas production kinetics of drought tolerant shrubs (Cassia sturtii, Atriplex nummularia and three Atriplex canescens cultivars, viz. Santa Rita, Field Reserve 1 and Rincon) growing under South African conditions (Hatfield in the Gauteng Province and Mier and Lovedale, both in the Northern Cape Province). Edible forage was incubated for 72 h to record in sacco neutral detergent fibre (NDF) degradability parameters and in vitro gas production. No significant difference was found between locations in terms of the NDF degradation parameters, except the NDF effective degradation (ED). However, the species differed in terms of the slowly degradable NDF fraction (NDF b-value) and rate of the degradation of NDF (NDF c-vlaue) in the Hatfield samples. Species differed significantly in terms of NDF ED value for samples collected at Mier. Species also differed in the rate of gas production (c) the volume of effective gas produced (EGP) and the potential extent of gas production (b) values. Atriplex nummalaria was ranked better than A. canescens (Field Reserve 1) in terms of NDF ED-value in Mier and NDF b-value in Hatfield, though the latter had shown higher c-values for samples collected in Hatfield. A similar trend was recorded in the gas production study, where A. canescens (Field Reserve 1) ranked least in terms of effective gas production and the potential extent of gas production compared to the other Atriplex species and C. sturtii. This indicates a lower feeding value of this cultivar as a ruminant feed compared to other Atriplex cultivars and C. sturtii.
Ruminal degradation and in vitro gas production characteristics of foliage from Atriplex species and Cassia sturtii
Author: W.A. van Niekerk, Abubeker Hassen, P.J. Vermaak, N.F.G. Rethman and R.J. Coertze
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