Natural products as manipulators of rumen fermentation

RJ Wallace, NR McEwan, FM McIntosh, B Teferedegne, CJ Newbold

Research output: Contribution to journalConference articlepeer-review

252 Citations (Scopus)


There is increasing interest in exploiting natural products as feed additives to solve problems in animal nutrition and livestock production. Essential oils and saponins are two types of plant secondary compounds that hold promise as natural feed additives for ruminants. This paper describes recent advances in research into these additives. The research has generally concentrated on protein metabolism. Dietary essential oils caused rates of NH3 production from amino acids in ruminal fluid taken from sheep and cattle receiving the oils to decrease, yet proteinase and peptidase activities were unchanged. Hyper-ammonia-producing (HAP) bacteria were the most sensitive of ruminal bacteria to essential oils in pure culture. Essential oils also slowed colonisation and digestion of some feedstuffs. Ruminobacter amylophilus may be a key organism in mediating these effects. Saponin-containing plants and their extracts appear to be useful as a means of suppressing the bacteriolytic activity of rumen ciliate protozoa and thereby enhancing total microbial protein flow from the rumen. The effects of some saponins seems to be transient, which may stem from the hydrolysis of saponins to their corresponding sapogenin aglycones, which are much less toxic to protozoa. Saponins also have selective antibacterial effects which may prove useful in, for example, controlling starch digestion. These studies illustrate that plant secondary compounds, of which essential oils and saponins comprise a small proportion, have great potential as 'natural' manipulators of rumen fermentation, to the potential benefit of the farmer and the environment.
Original languageEnglish
Pages (from-to)1458-1468
Number of pages11
JournalAsian-Australasian Journal of Animal Sciences
Issue number10
Publication statusPrint publication - 2002
Externally publishedYes
Event4th Korea/Japan Joint Symposium on Rumen Metabolism and Physiology - Jeju, Korea, Republic of
Duration: 21 May 200224 May 2002


  • Essential oils
  • Manipulation
  • Ruminants
  • Saponins


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