Use of selected tropical feeds and additives as modulators of rumen fermentation and methanogenesis in ruminants

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.