A wide range of plant bioactive components (phytochemicals) have been identified as having potential to modulate the processes of fermentation in the rumen. The use of plants or plant extracts as natural feed additives has become a subject of interest not only among nutritionists but also other scientists. Although a large number of phytochemicals (e.g. saponins, tannins and essential oils) have recently been investigated for their methane reduction potential, there have not yet been major breakthroughs that could be applied in practice. A key tenet of this paper is the need for studies on the influence of plant components on methane production to be performed with standardized samples. Where there are consistent effects, the literature suggests that saponins mitigate methanogenesis mainly by reducing the number of protozoa, condensed tannins both by reducing the number of protozoa and by a direct toxic effect on methanogens, whereas essential oils act mostly by a direct toxic effect on methanogens. However, because the rumen is a complex ecosystem, analysis of the influence of plant components on the populations of methanogens should take into account not only the total population of methanogens but also individual orders or species. Although a number of plants and plant extracts have shown potential in studies in vitro, these effects must be confirmed in vivo.

The interactions of lauric (C₁₂) and myristic acid (C₁₄) in suppressing ruminal methanogenesis and methanogens were investigated with the rumen simulation technique (Rusitec) using bovine ruminal fluid. The fatty acids were added to basal substrates (grass hay:concentrate, 1:1.5) at a level of 48 g/kg DM, provided in C₁₂:C₁₄ratios of 5:0, 4:1, 3:2, 2·5:2.5, 2:3, 1:4 and 0:5. Additionally, an unsupplemented control consisting of the basal substrates only was employed. Incubation periods lasted for 15 (n4) and 25 (n2) d. CH₄formation was depressed by any fatty acid mixture containing at least 40 % C₁₂, and effects persisted over the complete incubation periods. The greatest depression (70 % relative to control) occurred with a C₁₂:C₁₄ratio of 4:1, whereas the second most effective treatment in suppressing CH₄production (60 % relative to control) was found with a ratio of 3:2. Total methanogenic counts were decreased by those mixtures of C₁₂and C₁₄also successful in suppressing methanogenesis, the 4:1 treatment being most efficient (60 % decline). With this treatment in particular, the composition of the methanogenic population was altered in such a way that the proportion ofMethanococcalesincreased andMethanobacterialesdecreased. Initially, CH₄suppression was associated with a decreased fibre degradation, which, however, was reversed after 10 d of incubation. The present study demonstrated a clear synergistic effect of mixtures of C₁₂and C₁₄in suppressing methanogenesis, mediated probably by direct inhibitory effects of the fatty acids on the methanogens.

This study was undertaken to determine mineral content, amino acid and fatty acid composition of the freshwater macroalga – Cladophora glomerata. The studies were based on the content comparison in algal biomass collected from a lake and cultured in a laboratory. To determine the ability of copper cumulating by macroalgae, Cladophora was cultured in the medium supplemented with Cu ions. This study indicated that the relative abundance of metals in filaments decreased in the following order: Ca > K > Mg > Na > Fe > Cu > Zn > Pb > As > Ni > Cd > Mn > Cr > Co. Total protein content ranged from 14.45% in Cladophora from a lake to 26.55% in Cladophora from a laboratory. The main amino acids analyzed were aspartic and glutamic acid. The fatty acid content in the dry matter of the extract varied depending on the extraction method used: ethylene alcohol (19.0%), acetone (34.5%) or supercritical fluid extraction (62.5%). Freshwater C. glomerata due to the macrominerals, trace elements, amino and fatty acids composition in the extracts can be a valuable resource for nutritional and cosmetic applications.