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, eg 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

The Rumen Protozoa

Decreasing enteric methane (CH4) emissions from ruminants without altering animal production is desirable both as a strategy to reduce global greenhouse gas (GHG) emissions and as a means of improving feed conversion efficiency. The aim of this paper is to provide an update on a selection of proved and potential strategies to mitigate enteric CH4 production by ruminants. Various biotechnologies are currently being explored with mixed results. Approaches to control methanogens through vaccination or the use of bacteriocins highlight the difficulty to modulate the rumen microbial ecosystem durably. The use of probiotics, i.e. acetogens and live yeasts, remains a potentially interesting approach, but results have been either unsatisfactory, not conclusive, or have yet to be confirmed in vivo. Elimination of the rumen protozoa to mitigate methanogenesis is promising, but this option should be carefully evaluated in terms of livestock performances. In addition, on-farm defaunation techniques are not available up to now. Several feed additives such as ionophores, organic acids and plant extracts have also been assayed. The potential use of plant extracts to reduce CH4 is receiving a renewed interest as they are seen as a natural alternative to chemical additives and are well perceived by consumers. The response to tannin- and saponin-containing plant extracts is highly variable and more research is needed to assess the effectiveness and eventual presence of undesirable residues in animal products. Nutritional strategies to mitigate CH4 emissions from ruminants are, without doubt, the most developed and ready to be applied in the field. Approaches presented in this paper involve interventions on the nature and amount of energy-based concentrates and forages, which constitute the main component of diets as well as the use of lipid supplements. The possible selection of animals based on low CH4 production and more likely on their high efficiency of digestive processes is also addressed. Whatever the approach proposed, however, before practical solutions are applied in the field, the sustainability of CH4 suppressing strategies is an important issue that has to be considered. The evaluation of different strategies, in terms of total GHG emissions for a given production system, is discussed.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/EA3281B79CF2653DF2D1CD946D698D1A/S1751731109990620a.pdf/div-class-title-methane-mitigation-in-ruminants-from-microbe-to-the-farm-scale-div.pdf

Methane mitigation in ruminants: from microbe to the farm scale

Worldwide occurrence of mycotoxins in commodities, feeds and feed ingredients

Development of a real-time PCR assay for monitoring anaerobic fungal and cellulolytic bacterial populations within the rumen.

https://cyberleninka.org/article/n/1082452.pdf

Invited review: Enteric methane in dairy cattle production: Quantifying the opportunities and impact of reducing emissions

The aim of this paper is to review the role of methane in the global warming scenario and to examine the contribution to atmospheric methane made by enteric fermentation, mainly by ruminants. Agricultural emissions of methane in the EU-15 have recently been estimated at 10.2 million tonnes per year and represent the greatest source. Of these, approximately two-thirds come from enteric fermentation and one-third from livestock manure. Fermentation of feeds in the rumen is the largest source of methane from enteric fermentation and this paper considers in detail the reasons for, and the consequences of, the fact that the molar percentage of the different volatile fatty acids produced during fermentation influences the production of methane in the rumen. Acetate and butyrate promote methane production while propionate formation can be considered as a competitive pathway for hydrogen use in the rumen. The many alternative approaches to reducing methane are considered, both in terms of reduction per animal and reduction per unit of animal product. It was concluded that the most promising areas for future research for reducing methanogenesis are the development of new products/delivery systems for anti-methanogenic compounds or alternative electron acceptors in the rumen and reduction in protozoal numbers in the rumen. It is also stressed that the reason ruminants are so important to mankind is that much of the world's biomass is rich in fibre. They can convert this into high quality protein sources (i.e. meat and milk) for human consumption and this will need to be balanced against the concomitant production of methane.

/pdf/methane-production-by-ruminants-its-contribution-to-global-2hwron4syv.pdf

Methane production by ruminants: its contribution to global warming

Methods for preventing, decontaminating and minimizing the toxicity of mycotoxins in feeds

In vitro and in vivo fermentation of glycerol by rumen microbes

A simple analytical procedure derived from that described by Zinn and Owens (1980), based on the determination of nucleic purine bases (RNA eq), was carried out to measure microbial nitrogen flow in the ruminant duodenum. Several procedures for sample preservation were tested; the efficiency of each step of the analytical method was also determined using high performance liquid chromatography (HPLC). The proposed method (RNA eq) was compared with two other methods considered as references (2-6 diaminopimelic acid and 35S incorporation) and microbial nitrogen flow was measured in defaunated sheep. The recovery of purine bases analysed by the Zinn and Owens method was generally good (101% pure bases; 90% when bases were added to bacterial samples; 96% when added to yeast RNA). The HPLC measurements allowed us to conclude that this spectrophotometric method is specific for purine bases, all pyrimidine bases being eliminated. Moreover, it was found that the method must be used on freeze-dried samples; storage at + 4 degrees C, defatting or freezing gave incorrect results. Using the described assay, we observed that microbial nitrogen flow at the duodenum of defaunated sheep was not significantly different from that obtained using more traditional markers such as sulphur-35 incorporation or diaminopimelic acid.

/pdf/determination-of-assay-parameters-for-rna-analysis-in-1pfigghf29.pdf

Determination of assay parameters for RNA analysis in bacterial and duodenal samples by spectrophotometry. Influence of sample treatment and preservation.

Publisher Summary This chapter describes the results from digestion trials with defaunated and faunated animals as well as attempts to deduce the specific roles of various protozoa in rumen digestion. Scientists are beginning to understand the role of ciliate protozoa in rumen digestion, the specific functions of species, and their relation to animal production . Comparisons between methods used to defaunate are essential to obtain reliable results. Currently, no method is able to control the population of protozoa in farm conditions. The chapter also describes the generic composition of protozoa population in the rumen.. Ciliate protozoa are an integrated part of the rumen and the ruminant system. The complexity of interactions within this system is such that defaunation can initiate a series of interrelated effects in ruminant metabolism beyond rumen digestion. The overall effects must be taken into account to assess the real advantages for animals of controlling protozoal population in the rumen.

J. P. Jouany

Papers

Methane production by ruminants: its contribution to global warming

Methods for preventing, decontaminating and minimizing the toxicity of mycotoxins in feeds

In vitro and in vivo fermentation of glycerol by rumen microbes

Determination of assay parameters for RNA analysis in bacterial and duodenal samples by spectrophotometry. Influence of sample treatment and preservation.

Effects of the presence or absence of rumen protozoa on the efficiency of utilisation of concentrate and fibrous feeds