Rumen fermentations, products

Metges, C, Kempe K. and Schmidt, H.-L. 1990 Dependence of the carbon-isotope contents of breath carbon dioxide, milk, serum and rumen fermentation products on the 8 Cvalue of food in dairy cows. British Journal ofNutritim 63 187-196. 

In animals, cobalt only occurs as a component of vitamin B-12 (properly called cyanoco-balamin). All animals use vitamin B-12 in amino acid metabolism and red blood cell formation, and ruminants especially use it for converting rumen fermentation products into glucose in the liver. But again, plants do not have red blood cells, rumens, or livers, and thus have no need for either vitamin B-12 or any other molecules that contain cobalt. 

In mminants, whose main metabohc fuel is short-chain fatty acids formed by bacterial fermentation, the conversion of propionate, the major glucogenic product of rumen fermentation, to succinyl-CoA via the methyhnalonyl-CoA pathway (Figure 19—2) is especially important. 

Hungate RE. 1976. The rumen fermentation. In Schlegel HG, Gottschalk G, Pfennig N, editors. Microbial production and utihzation of Gases. Gottingen Goltze. p 119-24... 

One product of the rumen fermentation, methane, is of no value to the ruminant. The major fermentation products used by the ruminant are the short-chain fatty acids, acetate, butyrate and propionate. Acetate and butyrate can be used for energy, but propionate is most useful for the synthesis of protein. If the fermentation could be shifted to reduce methane, acetate and butyrate production and to increase the propionate, the feed efficiency and growth rate could improved. 

Three broad groupings, of the antibiotic substances presently used in animal production, include (a) broad-spectrum antibiotics, including penicillins and tetracyclines, which are effective against a wide variety of pathogenic and non-pathogenic bacteria (b) several narrow-spectrum antibiotics that are not used in human medicine and. (c) the ionophore antibiotics, monensin. lasalocid and salinomycin Monensin and lasalocid are used as rumen fermentation regulators in beef cattle, and the three ionophores are used as coccidiostats in poultry production. The ionophores. which are not used in human medicine, were first introduced in the 1970 s and account for most of the increase in antibiotic usage in animal production since the 1960 s. 

Yarlett N (1994) Fermentation product generation in rumen chytridiomycetes. In Mountfort DO, Orpin CG (eds) Anaerobic fungi. Dekker, New York, pp 129-146 Yarlett N (2004) Anaerobic protists and hidden mitochondria. Microbiology 150 127-129 Yarlett N, Hackstein JHP (2005) Hydrogenosomes one organelle, multiple origins. Bioscience 55 657-668... 

Because the presence of CLA in the human diet is reliant on ruminant products, this chapter first addresses the synthesis of CLA in ruminants. The presence of CLA in ruminant milk and meat is related to rumen fermentation and its synthesis by microorganisms through the process of biohydrogenation (BH) of dietary unsaturated fatty acids. Thus, the effect of diet and processes within the rumen is reviewed. The role of endogenous synthesis of CLA in mammalian tissues has been discovered, and this will be discussed also first as it contributes to the occurrence of CLA in ruminant products and second the significance of endogenous synthesis as a source of CLA in humans and other species. 

In view of the encouraging results obtained by feeding alder sawdust to beef cattle, as was reported earlier, it seemed worthwhile to develop methods of treatment mat would make the cellulose in low quality roughages more available to rumen microorganisms. In order to assess the merits of various physical and chemical treatments of wood and wood by-products, in vitro rumen fermentation tests were conducted and the extent of availability of nutrients to the microorganisms studied. 

Ipharraguerre, I.R. J.H. Clark D.E. Freeman. Rumen fermentation and intestinal supply of nutrients in dairy cows fed rumen-protected soy products./. Dairy Sci. 2005, 88, 2879-2892. 

It has been suggested that through its effects on (1) rumen fermentation (some experiments have shown increased microbial growth and increased propionic acid production) and (2) cell metabolism (increased utilisation of carbohydrate and reduced lipid mobilisation), nicotinic acid may be a useful supplement to dairy cows, particularly in situations of subclinical ketosis. However, the experimental evidence is not consistent. Nicotinic acid does not always give positive responses in the rumen and increases in blood concentrations were not observed in all experiments. Current recommendations do not advocate the supplementation of dairy cow diets in order to increase milk yield and composition. 

The bacteria number 10 -10 ° per millilitre of rumen contents. Over 200 species have been identified, and for descriptions of them the reader is referred to the works listed at the end of this chapter. Most of these bacteria are non-spore-forming anaerobes. Table 8.3 lists a number of the more important species and indicates the substrate they utilise and the products of the fermentation. This information is based on studies of isolated species in vitro and is not completely applicable in vivo. For example, it appears from Table 8.3 that succinic acid is an important end product, but in practice this is converted into propionic acid by other bacteria such as Selenomonas ruminantium (see Fig. 8.6) such interactions between microorganisms are an important feature of rumen fermentation. A further point is that the activities of a given species of bacteria may vary from one strain of that species to another. The total... 

Table 8.3 Typical rumen bacteria, their energy sources and fermentation products in vitro...

As investigations have revealed the mechanisms of rumen digestion, attempts have been made to alter the patterns of digestion in ways that should improve the nutrition of ruminants. The primary approach has been to modify the microbial population in order to suppress undesirable processes (e.g. methane production see Section 8.4 and Chapter 11) or stimulate desirable processes (e.g. microbial protein synthesis). A secondary approach has been to protect nutrients from rumen fermentation in order that they should be digested in the small intestine. Changing the bacterial... 

In order to reduce the climatic influence of methane from agricultural sources, ways of reducing the production from rumen fermentation are being investigated. Substances added to the food to decrease methane production include halogen analogues of methane. However, their effects tend to decrease over time as the rumen bacterial population adapts to their presence. lonophore antibiotics (monensin see Chapter 24) decrease methane production and increase propionate formation and... 

The volatile fatty acids are absorbed through the rumen wall. Methane and carbon dioxide are by-products of rumen fermentation. 

MEferm is assumed to be 0.1 ME for silages and 0.05 ME for brewery and distillery by-products, and MEfat is 35 MJ/kg. The assumption made here for silage must be suspect. The major fermentation product in well-made silages is lactate, and there is evidence that several rumen bacteria, notably Megasphaera elsdenii (see Table 8.3 in Chapter 8), are able to utilise lactate with the production of propionate. The microbial crude protein yield (g) is calculated as follows ... 

There is some evidence (Fig. 16.4) that the efficiency of utilisation of metabolisable energy for milk production is influenced by the proportion of acetate in the fatty acids produced during rumen fermentation. 

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