Rumen microbes

CH4 emitted from manure depends primarily on (i) the management system such as solid disposal system, liquid disposal systems, e.g., ponds, lagoons, and tanks, which can emit up to 80% of manure-based CH4 emissions, while solid manure emits little or no CH4. (ii) Environmental conditions are also important. The higher the temperature and moisture, the more CH4 produced, (iii) CH4 emissions also depend on the quantity of the manure produced, which depends on the number of animals housed, the amount of feed the consumed, and the digestibility of the feed, (iv) Manure characteristics depend on the animal type, feed quality, and rumen microbes present in the rumen and digestive tracks. Manure handled in liquid form tends to release more amount of CH4 when compared to solid or manures thrown into the pasture, which do not decompose anaerobically. High temperatures with neutral pH and high moisture content enhance CH4 production [45],... 

Waghom GC, Stafford KJ. Gas production and nitrogen digestion by rumen microbes from deer and sheep. New Zealand Journal Agricultural Research. 1993 36 493-497. 

Previously it was reported (41) that dry heating of alfalfa at lOS C for up to 1440 min resulted in a reduction of in vitro organic matter digestibility (IVOMD) by rumen microbes. Increases in Acid Detergent Insoluble N (ADIN) and Neutral Detergent Fibre (NDF) were also observed. For the convenience of the reader these data have been included with more recent observations in this study. 

Fatty acids are the building blocks of TAG. More than 90 percent of fatty acids have an even number of carbon atoms, and are in aliphatic chains ranging from 4 to 22 carbons in length. The major fatty acid synthesis pathway is production of stearic acid (18 carbons) after which separate desaturase systems introduce 1, 2, or 3 unsaturated (double) bonds. Additional enzymes become active in elongating the chain as needed. Shorter fatty acids also are produced. Trace amounts of odd-number carbon fatty acids are found in most fats, and also have been synthesized for research purposes. Microorganisms frequently produce odd-number carbon fatty acids, with heptadecenoic (17 carbon) acid a major component of Candida tropicalis yeast fat. Up to 8 percent C17 fatty acids have been found in milk and meat fats of ruminants (cattle, sheep, goats) and are of rumen microbe origin. 

Van Soest, P. J. (1982). Rumen microbes. In "Nutritional ecology of the ruminant Ruminant metabolism, nutritional strategies, the cellulolytic fermentation and the chemistry of forages and plant fibers." Chap.10. In "Part IV Gastrointestinal Fermentations." Comstock Publishing Associates, Ithaca and London. 

White BA, Cann IKO, Mackie RI, Morrison M (1997) Cellulase and xylanase genes from ruminal bacteria domain analysis suggests a non-cellulosome-like model for organization of the cellulase complex. In Onodera R, Itabashi H, Ushida K, Yano H,Sasaki Y (eds) Rumen microbes and digestive physiology in ruminants. Jpn Sci Soc Press, Tokyo, p 69... 

The ruminant animal and rumen microorganisms exist in a reciprocally beneficial relationship, in which cellulose and other plant carbohydrates are fermented by the rumen microbes to form chiefly C02 and volatile fatty acids (VFA). The microorganisms are adapted to live between pH 5.5 and 7.0, in the absence of oxygen,... 

When fats are fed to an animal with a rnmen, they are exposed to rumen microbes in an environment that contains lots of excess hydrogen (low pH) and no free oxygen. The rnmen bacteria and protozoa don t metabolize fat directly—they are unable to use the fats for their own energy—bnt they can alter the strnctnre of some fats. 

The rumen microbes thus have a levelling effect on the protein supply of the ruminant they supplement, in both quantity and quality, the protein of such foods as low-quality roughages but have a deleterious effect on protein-rich concentrates. It is possible to take additional advantage of the synthesising abilities of the rumen bacteria by adding urea to the diet of ruminants (see below). A more recent development, discussed on p. 186, is the protection of good-quality proteins from degradation in the rumen. 

The capacity of rumen microorganisms to digest lipids is strictly limited. The lipid content of ruminant diets is normally low (i.e. <50 g/kg), and if it is increased above 100 g/kg the activities of the rumen microbes are reduced. The fermentation of fibre is retarded and food intake falls. Saturated fatty acids affect rumen fermentation less than do unsaturated fatty acids. Calcium salts of fatty acids have little effect on rumen fermentation and are used as fat supplements for ruminants. 

The ATP yield (mol/kg DM) is converted by the rumen microbes to produce microbial DM. The efficiency of this conversion (Yatp g microbial DM per mol ATP) is determined by the growth rate of the microbes, with faster-growing microbes using the energy more efficiently than those growing more slowly. The rate of growth of the microbes is determined by the phase with which they associate (i.e. soluble/small particles, forage or concentrate particles) and its outflow rate from the rumen and is calculated as follows ... 

Finally, to convert microbial DM to microbial protein, it is assumed that rumen microbes contain 100 gN/kg DM and that microbial crude protein consists of 160 g N/kg DM, providing a microbial crude protein content of 625 g/kg microbial DM. Microbial crude protein is converted to digestible microbial true protein by multiplying by 0.6375, as described earlier. 

The UK metabolisable protein system divides the requirement of an animal into that which is required for supplying the needs of the rumen microbes and that which is required at tissue level. After estimating the contribution of microbial protein to satisfying this demand, the requirement for undegraded dietary protein is calculated. 

Protein requirements for ruminant animals are stated in terms of metabolisable protein, and protein supply to rumen microbes are expressed in terms of effective rumen-degrad-able (ERDP) protein or effective rumen-degradable nitrogen (EDN). 

In recent years the proximate analysis procedure has been severely criticised by many nutritionists as being archaic and imprecise, and in the majority of laboratories it has been partially replaced by other analytical procedures. Most criticism has been focused on the crude fibre, ash and nitrogen-free extractives fractions for the reasons described above. The newer methods have been developed to characterise foods in terms of the methods used to express nutrient requirements. In this way, an attempt is made to use the analytical techniques to quantify the potential supply of nutrients from the food. For example, for ruminants, analytical methods are being developed that describe the supply of nutrients for the rumen microbes and the host digestive enzyme system (Fig. 1.1). 

Broudiscou LP, Papon Y, Brodiscou AF (2000) Effects of dry plant extracts on fermentation and methanogenesis in continuous culture of rumen microbes. Anim Feed Sci Technol 87 263-277... 

Maia MRG, Chaudary LC, Bestwick CS, Richardson AJ, McKain N, Larson TR, Graham lA, Wallace RJ (2010) Toxicity of unsaturated fatty acids to the biohydrogenating ruminal bacterium, Butyrivibrio flbrisolvens. BMC Microbiol 10 52. doi 10.1186/1471-2180-10-52 Makkar HPS, Becker K (1997) Degradation of quUlaja saponins by mixed culture of rumen microbes. Lett Appl Microbiol 25 243-245... 

There are several recent reviews on the effect of secondary compounds including saponin or saponin containing plants on rumen function and animal production (Hart et al. 2008 Patra and Saxena 2009a). This review describes in more details saponin extraction methods, the stmctural diversity of saponins and their effect on rumen microbes and rumen fermentation. The information presented here could provide wider opportunities for the utilization of saponins and saponin-containing plants as feed additives in sustainable and environmental friendly ruminant production. 

Rumen microbes produce a variety of intracellular or extracellular enzymes. These enzymes hydrolyse all substances at different rates. Saponins are glycosylated compounds and are highly soluble in water or aqueous medium. Saponins can dissolve easily in the rumen and therefore be readily degraded by the various glycosidases... 

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