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The role of ciliate protozoa in the rumen.

Newbold, Charles J.; de la Fuente, Gabriel; Belanche, Alejandro; Ramos-Morales, Eva; McEwan, Neil R.


Charles J. Newbold

Gabriel de la Fuente

Alejandro Belanche

Eva Ramos-Morales

Neil R. McEwan


First described in 1843, Rumen protozoa with their striking appearance were assumed to be important for the welfare of their host. However, despite contributing up to 50% of the bio-mass in the rumen, the role of protozoa in rumen microbial ecosystem remains unclear. Phylogenetic analysis of 18S rDNA libraries generated from the rumen of cattle, sheep, and goats has revealed an unexpected diversity of ciliated protozoa although variation in gene copy number between species makes it difficult to obtain absolute quantification. Despite repeated attempts it has proven impossible to maintain rumen protozoa in axenic culture. Thus it has been difficult to establish conclusively a role of ciliate protozoa in rumen fiber degradation. The development of techniques to clone and express ciliate genes in λ phage, together with bioinformatic indices to confirm the ciliate origin of the genes has allowed the isolation and characterization of fibrolytic genes from rumen protozoa. Elimination of the ciliate protozoa increases microbial protein supply by up to 30% and reduces methane production by up to 11%. Our recent findings suggest that holotrich protozoa play a disproportionate role in supporting methanogenesis whilst the small Entodinium are responsible for much of the bacterial protein turnover. As yet no method to control protozoa in the rumen that is safe and practically applicable has been developed, however a range of plant extract capable of controlling if not completely eliminating rumen protozoa have been described.


NEWBOLD, C.J., DE LA FUENTE, G. BELANCHE, A. RAMOS-MORALES, E. and MCEWAN, N.R. 2015. The role of ciliate protozoa in the rumen. Frontiers in microbiology [online], 6, Article 1313. Available from:

Journal Article Type Article
Acceptance Date Nov 9, 2015
Online Publication Date Nov 26, 2015
Publication Date Dec 31, 2015
Deposit Date Oct 1, 2018
Publicly Available Date Oct 1, 2018
Journal Frontiers in microbiology
Print ISSN 1664-302X
Electronic ISSN 1664-302X
Publisher Frontiers Media
Peer Reviewed Peer Reviewed
Volume 6
Article Number 1313
Keywords Rumen; Protozoa; Defaunation; Methane; Microbial diversity
Public URL


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