The Rumen Microbial Ecosystem

pp 73-139

The rumen protozoa

  • A. G. WilliamsAffiliated withHannah Research Institute
  • , G. S. ColemanAffiliated withBiochemistry Department, Babraham Institute

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In addition to the bacteria in the rumen there are many larger (5–250/mm long) organisms which at various times have been designated protozoa. Of these the ‘ovals’ (Quin’s and Eadie’s) are now known to be large bacteria (Orpin, 1976) and the ‘flagellates’ Neocallimastix frontalis, Piromonas communis and Sphaeromonas communis are the zoospores of phycomycete fungi (Orpin, 1977a, b). There are genuine flagellates in the rumen, e.g. Trichomonas spp., Monoceromonas sp. and Chilomastix sp., but almost nothing is known about their metabolism (Jensen and Hammon, 1964). The largest, most obvious and most important protozoa are the ciliates, of which there are two groups both in the subclass Trichostomatia. The so called ‘holotrich’ protozoa belong to the order Vestibuliferida and the entodiniomorphs to the order Entodiniomorphida, suborder Entodiniomorphina and family Ophryoscolecidae. As the properties and metabolism of these two protozoal groups are different, they will be considered separately below.