Abstract:
The main objective of this work was to identify potential rumen modulators or feed
additives that improve fibre digestion while reducing enteric methane production from
tropical feeds. The research was conducted in the Department of Animal and Wildlife
Sciences, University of Pretoria, South Africa. To accomplish this, feed additives and feeding
technologies that were tested elsewhere to reduce methane in various ruminant production
systems were reviewed in Chapter one. In Chapter two, the in vitro fermentability and
methane production of commonly used tropical perennial grasses were studied. In Chapter
three, 19 tropical browses collected from Pretoria were studied for their potential
fermentation and methane production under in vitro conditions. In Chapter four, three types of tannin-containing browse foliage that were collected from the Kalahari Desert in South
Africa were used to replace Medicago sativa hay in a total mixed ration fed to Merino rams
in order to investigate their effect on rumen fermentation and enteric methane production. In
Chapter five, cellulase and xylanase fibrolytic enzymes were studied for their feed
fermentation potential and methane production at seven dose rates. In Chapter six, the effects
of fibrolytic enzymes, nitrate and enzyme-nitrate mixture were evaluated by measuring
rumen fermentation and enteric methane production in Merino rams. Finally, general
conclusions, recommendations and critical evaluation based on this experimental work were
presented in Chapter seven.
