Fermentation Characteristics and Microbial Protein Synthesis in an In Vitro System Using Cassava, Rice Straw and Dried Ruzi Grass as Substrates

  • Sommart, K. (Faculty of Agriculture, Khon Kaen University) ;
  • Parker, D.S. (Faculty of Agriculture & Biological Sciences, University of Newcastle upon Tyne) ;
  • Rowlinson, P. (Faculty of Agriculture & Biological Sciences, University of Newcastle upon Tyne) ;
  • Wanapat, M. (Faculty of Agriculture, Khon Kaen University)
  • Received : 1999.05.20
  • Accepted : 1999.11.30
  • Published : 2000.08.01


An in vitro gas production system was used to investigate the influence of various substrate mixtures on a natural mix of rumen microbes by measurement of fermentation end-products. The treatments were combinations of cassava (15.0, 30.0 and 45.0%) with different roughage sources (ruzi grass, rice straw or urea treated rice straw). Microbial biomass, net $^{15}N$ incorporation into cells, volatile fatty acid production, gas volume and rate of gas production increased linearly with increasing levels of cassava inclusion. There was also an effect of roughage source, with rice straw being associated with the lowest values for most parameters whilst similar values were obtained for ruzi grass and urea treated rice straw. The results suggest that microbial growth and fermentation rate increase as a function of readily available carbohydrate in the substrate mixture. A strong linear relationship between $^{15}N$ enrichment, total volatile fatty acid production and gas production kinetics support the suggestion of the use of the in vitro gas production system as a tool for screening feedstuffs as an initial stage of feed evaluation.


In Vitro Gas Production;Fermentation;Microbial Protein Synthesis;Rumen

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