Feeding saponin-containing Yucca schidigera and Quillaja saponaria to decrease enteric methane production in dairy cows

Mitigation of greenhouse gas emissions in the production of fluid milk

Global climate change, driven by the buildup of greenhouse gas (GHG) emissions in the atmosphere, is challenging the dairy industries in the United States and throughout the world to develop sustainable initiatives to reduce their environmental impact. The U.S. dairy industry has committed to lowering the GHG emissions, primarily CH(4), N(2)O, and CO(2), in each sector of the fluid milk supply chain which extends from the farm, to the processing plant, and to distribution of the packaged product, where it is refrigerated by the retailer and then the consumer. This chapter provides an overview of the life cycle analysis (LCA) technique and its use in identifying the GHG emissions in each sector of the fluid milk supply chain, from cradle to grave, and the best practices and research that is currently being conducted to reduce or mitigate GHG emissions in each sector. We also discuss the use of on-farm and off-farm process simulation as tools for evaluating on-farm mitigation techniques, off-farm alternative processing scenarios, and use of alternative energy management practices.

Methanogens: methane producers of the rumen and mitigation strategies

Methanogens are the only known microorganisms capable of methane production, making them of interest when investigating methane abatement strategies. A number of experiments have been conducted to study the methanogen population in the rumen of cattle and sheep, as well as the relationship that methanogens have with other microorganisms. The rumen methanogen species differ depending on diet and geographical location of the host, as does methanogenesis, which can be reduced by modifying dietary composition, or by supplementation of monensin, lipids, organic acids, or plant compounds within the diet. Other methane abatement strategies that have been investigated are defaunation and vaccines. These mitigation methods target the methanogen population of the rumen directly or indirectly, resulting in varying degrees of efficacy. This paper describes the methanogens identified in the rumens of cattle and sheep, as well as a number of methane mitigation strategies that have been effective in vivo.

Fermentation characteristics of corn-, triticale-, and wheat-based dried distillers' grains with solubles in barley-based diets determined using continuous and batch culture systems

BACKGROUND

Dried distillers' grains with solubles (DDGS) are becoming increasingly available and popular as an alternative livestock feed. This study used continuous and batch culture techniques to compare the in vitro fermentation characteristics of diets containing corn-, triticale- or wheat-based DDGS at 200 g kg(-1) diet dry matter (DM) against a barley grain-based control diet.

RESULTS

In continuous fermentation of wheat DDGS diet, total volatile fatty acid (VFA) concentration was decreased by 15.7% across sampling times and NH(3) concentration was quadrupled compared with control, whereas fermentations of corn- and triticale-DDGS diets were similar to the barley-based control. In batch cultures, corn DDGS differed from control only in increased culture pH. Compared with control diet, triticale DDGS yielded lower total gas production (140.94 versus 148.78 mL g(-1) DM) and in vitro DM digestibility (IVDMD; 0.509 versus 0.535). Wheat DDGS diet yielded decreased total gas production (123.49 mL g(-1) DM) and IVDMD (0.468), as well as total VFA production (105.84 versus 134.20 mmol L(-1)) and substantially increased ammonia concentration (151.61 versus 58.34 mg L(-1)) and acetate:propionate ratio (2.94 versus 1.11).

CONCLUSION

Corn- and triticale- DDGS diets exhibited fermentation characteristics similar to the barley based control diet, consistent with in vivo findings that these diets yielded no adverse effects on production. In vitro ruminal fermentation of wheat DDGS diet differed significantly from control in several aspects including 2.6 to 6X higher ammonia concentrations.

A new perspective on the use of plant secondary metabolites to inhibit methanogenesis in the rumen

Recently, greenhouse gas emissions have been of great concern globally. Ruminant livestock due to production of methane during normal fermentation in the rumen contributes substantially to the greenhouse effects. During the recent decade, a paradigm shift has been initiated whether plant secondary metabolites (PSM) could be exploited as natural safe feed additives alternative to chemical additives to inhibit enteric methanogenesis. More than 200,000 defined structures of PSM have been known. Some plants or their extracts with high concentrations of bioactive PSM such as saponins, tannins, essential oils, organosulphur compounds, flavonoids and many other metabolites appear to have potential to inhibit methane production in the rumen. The possible mechanisms and effects of many PSM on rumen methanogenesis are not clearly understood. Saponins may decrease methanogenesis through the inhibition of rumen protozoa and in turn may suppress the numbers and activity of methanogens. Although the direct effect of saponins on methanogens has not been demonstrated, saponins might inhibit methanogens at high doses. Tannins may inhibit the methanogenesis directly and also via inhibition of protozoal growth. Essential oils, organosulphur compounds and flavonoids appear to have direct effects against methanogens, and a reduction of protozoa associated methanogenesis probably plays a minor role for these metabolites. The chemical structure and molecular weight of the PSM and chemical composition of diets dependent upon the different feeding regimes may influence the effects of PSM on methane production. Although PSM may negatively affect nutrient utilization, there is evidence that methanogenesis could be suppressed without adversely affecting rumen fermentation, which could be exploited to mitigate methane emission in ruminants.

The effect and mode of action of saponins on the microbial populations and fermentation in the rumen and ruminant production

The growing public concerns over chemical residues in animal-derived foods and threats of antibiotic-resistant bacteria have renewed interest in exploring safer alternatives to chemical feed additives in ruminant livestock. Various bioactive phytochemicals including saponins appear to be potential 'natural' alternatives to 'chemical' additives in modulating rumen fermentation favourably and animal performance. Saponins are a diverse group of glycosides present in many families of plants. The primary effect of saponins in the rumen appears to be to inhibit the protozoa (defaunation), which might increase the efficiency of microbial protein synthesis and protein flow to the duodenum. Furthermore, saponins may decrease methane production via defaunation and/or directly by decreasing the activities (i.e. rate of methanogenesis or expression of methane-producing genes) and numbers of methanogens. Saponins may also selectively affect specific rumen bacteria and fungi, which may alter the rumen metabolism beneficially or adversely. The ammonia-adsorption and modulation of digesta passage in the rumen by saponins have also been implicated in altering rumen metabolism, but their physiological responses are likely to be negligible compared with microbiological effects. The effects of saponins on rumen fermentation have not been found to be consistent. These discrepancies appear to be related to the chemical structure and dosage of saponins, diet composition, microbial community and adaptation of microbiota to saponins. There is need for systematic research based on chemical structures of saponins, nutrient composition of diets and their effects on rumen microbial ecosystem to obtain consistent results. The present paper reviews and discusses the effects and mode of action of saponins on microbial community and fermentation in the rumen, and ruminant performance.