The Role of Ciliate Protozoa in the Rumen

Abstract

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.

Supplementation of rapeseed and linseed oils to sheep rations: effects on ruminal fermentation characteristics and protozoal populations

“…Moreover, Isotrichidae as well as cellulolytic ciliates disappeared from the rumen of sheep fed an "oil" ration after 10 and 21 days, respectively. Newbold et al (2015) suggested that ruminal ciliates digest as well as convert dietary fat, but a high lipid concentration in the ration is toxic to protozoa. Szumacher-Strabel (2010) reported that the genus Epidinium spp.…”

“…(E. ecaudatum and E. caudatum) participated in 30% of lipolysis process, but these ciliates were not identified in our study. According to Newbold et al (2015) the antiprotozoal effect of fat depends on the fatty acid composition. Medium chain fatty acids are more effective in controlling ciliate amount than polyunsaturated fatty acids.…”

“…These authors reported that lauric acid (C12:0) may reduce the number of protozoa by 40%. Moreover, Hook et al (2010) andNewbold et al (2015) pointed out that other chemicals such as cooper sulfate, alkanates, calcium peroxide, ionophores as well as saponin may be toxic for protozoa. The strong decrease in the number of Entodinium spp., when sheep were fed rapeseed oil, was associated with microbial degradation of starch in the rumen (P = 0.062).…”

The Effect of Live Yeast Supplementation on Beef Cattle Performance: A Systematic Review and Meta-Analysis

“…Furthermore, some protozoa groups have fibrolytic activity and play a key role in the early colonization of the fibre (Newbold, Fuente, Belanche, Morales, & McEwan, 2015). Their defaunation also decreases the fibrolytic microorganism concentration in the rumen (Newbold et al, 2015).…”

Bakteri Denitrifikasi Inaktif Sebagai Suplemen Untuk Mengurangi Gas Metana dari Cairan Rumen Sapi

“…Selain itu, protozoa sebagai predator diperlukan sebagai pengendali komunitas mikroorganisme di dalam rumen. Eliminasi protozoa ciliata meningkatkan suplai protein (dari mencerna protein bakteri) hingga 30%, dan mengurangi produksi metana hingga 11% [25].…”