Metabolism in the Rumen

The initial step in rumen biohydrogenation of linoleic and linolenic acids involves an isomerization of the cis-12 double bond to a trans-11 

Isomer Ruminal outflow (g/day) Isomer Ruminal outflow (g/day) 

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Vernon, R.G. (1981). Eipid metabolism in the rumen. In Lipid Metabolism in the Adipose Tissue of Ruminant Animals, ed. Christie, W.W., Pergamon, Oxford, pp. 279-362. 

Metabolism may be mediated by intestinal microflora, epithelial enzymes, or liver enzymes preceding entry into the systemic circulation. Chloramphenicol is well absorbed when administered orally to calves less than 1 week old, but it is inactivated by microflora when administered to ruminants. Similar observations have been made after oral administration of amoxicillin, ampicillin, and cephalexin therapy in young calves (11). On the other hand, trimethoprim, which is extensively metabolized in the liver and may undergo some metabolism in the rumen, shows higher systemic availability in the newborn calf and kid, due probably to the lower metabolic activity in the neonatal animal. 

Harfoot, C.G. 1981. Lipid metabolism in the rumen. In Lipid Metabolism in Ruminant Animals (W.W. Christie, ed.), pp. 21-55, Pergamon Press Ltd., Oxford, UK. 

Although the first-pass effect is a major source of species variation in systemic availability of orally administered drugs that undergo extensive hepatic metabolism, another important source of variation is metabolism by ruminal microorganisms. Some drugs (nitroxynil, chloramphenicol, digitalis glycosides) are metabolized in the rumen to such an extent that parenteral administration is required for clinical efficacy. 

Because the metabolism of trans-18 1 to stearic acid is thought to be the rate-limiting step in complete BH (Keeney, 1970), the effects of diet on lipid metabolism in the rumen tend to have a more pronounced effect on the amount and relative proportions of trans-18 1 leaving the rumen than on other BH intermediates including isomers of CLA. With respect to enhancing RA content of ruminant foods, it could be argued that the most important aspects of dietary effects on ruminal BH relate to those on VA and the factors that regulate its synthesis. 

Latham, M.J., Storry, J.E., and Sharpe, M.E. 1972. Effect of low-roughage diets on the microflora and lipid metabolism in the rumen. Appl Microbiol. 24, 871-877. 

As the purpose of this in vitro experiment was to establish treatment guide-lines for subsequent animal feeding trials, the practicality of the various NaOH levels and dilutions was stressed. Ideally, both the amount of NaOH and water should be minimized in large-scale treatment procedures. Excess alkali either must be removed by washing as in the classical Beckmann procedure or alternatively, if neutralized by acid, the resultant sodium levels must not overload the animal s ability to maintain acid-base equilibrium (assuming acetate will be metabolized in the rumen). Use of large amounts of water should also be avoided as the final treated material would have to be dried prior to storage. 

Buccioni, A., Decandia, M., Minieri, S., MoUe, G., Cabiddu, A. (2012). Lipid metabolism in the rumen new insights on lipolysis and biohydrogenation with an emphasis on the role of endogenous plant factors. Animal Feed Science and Technology, 174, 1-25. 

Jenkins, T. C. (1993). Lipid metabolism in the rumen. Journal of Dairy Science, 76, 3851-3863. 

Harfoot, C.G., and G.P. Hazelwood. Lipid Metabolism in the Rumen, in The Rumen Microbial Ecosystem, Hobson, RN., Elsevier Science Publishing, New York, pp 285-322 (1988). 

Keeney, M. (1970) Lipid Metabolism in the Rumen, in Physiology of Digestion and Metabolism in the Ruminant (Phillipson, A.T., ed.) pp. 489-503, Oriel Press, Newcastle-upon-Tyne, UK. 

Source After Annison E F and Lewis D 1959 Metabolism in the Rumen, London, Methuen and Co. 

Naturally occurring isoflavones and coumestans have relatively weak oestrogenic activity, but this activity can be increased as a result of metabolism in the rumen. For example, the main isoflavone in subterranean clover, formononetin, is converted to equol in the rumen. Some plants, e.g. T. repens (white clover), are normally non-oestrogenic but when infected with fungi can produce high concentrations of coumestan. 

Proteolytic bacteria were present in relatively high numbers (10 /g of digetsa) in sheep fed on Calliandra leaves (McSweeney et al. 1999). The changes in the activities of proteolytic bacteria and the protease enzyme by tannins conld mediate nitrogen metabolism in the rumen (Tanner et al. 1994). A reduction in proteolysis might be attributed to the direct effects of CT on microbial proteolytic enzyme activity or... 

Influence of Essential Oils on Protein Metabolism in the Rumen... 

Harfoot CG, Hazlewood GP (1988) Lipid metabolism in the rumen. In Hobson PN, Stewart CS (eds) The rumen microbial ecosystem, 2nd edn. Bladde Academic Professional, New York Hart KJ, Yanez-Ruiz DR, Duval SM, McEvan NR, Newbold CJ (2(X)8) Plant extracts to manipulate rumen fermentation. Anim Feed Sd Technol 147 8-35 Heath IB, Bauchop T, Skipp RA (1983) Assignment of the rumen anaerobe Neocallimastix frontalis to the Spizellomycetales (Chytridiomycetes) on the basis on its polyflageUate zoospore ultrastructure. Can J Bot 61 295-307... 

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