Omasum, microorganisms

Finally, the contents of the omasum, now a thick slurry of microorganisms, pass into the abomasum into which are secreted acid and proteinases to produce an environment corresponding to that of the human stomach. Some of the microflora passing from the rumen to the omasum die and are digested by the acid and the enzymes. This provides the ruminant not only with an additional energy source but with vitamins and essential amino acids that its own tissues caimot synthesise. 

Although the transformation of C20 5 and C22 6 by ruminal microorganisms to other fatty acids is evident, the nature of the intermediates and endproducts is less clear. When fish oil was fed to dairy cows, no increase in the flow of any cis, trans CLA to the omasum was observed, including the cis-9, trans-W Cl8 2 isomer (23). However, increased omasal flows of trans-9, transA 1 CLA and several nonconjugated dienes were seen. Several studies reported the accumulation of transAl Cl8 1 in ruminal cultures (53) and omasal contents of cows (23), indicating the potential of the fish oil fatty acids to promote cis-9, trans-W production in body tissues and milk from desaturase activity. 

Ruminant A mammal that possesses four compartments in the stomach (rumen, reticulum, omasum, abomasum) and is capable of digesting fiber-rich foods. The rumen contains a wide range of anaerobic microorganisms capable of converting cellulose and other fibers—except lignin—into volatile fatty acids that are used as a source of energy. 

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