Abstract:
The nutritional value of browse foliage from the Thorny Kalahari Dune Bush veld of
South Africa is not characterized. Most of this browse species is rich in tannin, but still palatable,
and is consumed by ruminants during the dry season, as well as having a role to play in mitigating
enteric methane emission from ruminants. In this study, the rumen methane mitigation potential
of 19 browse species foliage collected from the Thorny Kalahari Dune Bush veld, was analyzed
in terms of chemical composition, in vitro fermentation, digestibility and methane production. In
vitro gas and methane production and organic matter digestibility (IVOMD) were determined by
using rumen fluid collected, strained and anaerobically prepared. A semi-automated system was
used to measure gas production (GP) from each browse species by incubating 400 mg samples
in a shaking incubator at 39 °C with or without inclusion of 400 mg of polyethylene glycol (PEG).
Data for all the parameters collected were statistically analyzed using the SAS (9.0) general
linear model (GLM) procedure, and differences between foliage species were determined using
Duncan’s multiple-range test. Acacia luederitzii and Monechma incanum showed the best potential
for decreasing methane production by up to 90 % after 48 h of incubation. The secondary
components (mainly tannins) of the browse species appeared to have a significant effect on
volatile fatty acids (VFA), methane and gas production as judged by the comparison of samples
incubated with or without PEG inclusion. The substantial amount of crude protein (CP) content
coupled with their anti-methanogenic effect during fermentation would make these browses a potential
mitigation option for small scale farmers and pastoralists in sub-Sahara Africa. However,
it is also very important that systematic and strategic supplementation in a mixed diet should be
looked at as the way forward in terms of best utilization.
