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(vertebrate zoology)
The third chamber of the ruminant stomach where the contents are mixed to a more or less homogeneous state. Also known as manyplies; psalterium.



one of the glandless sections in the multicompartmental stomach of ruminants (it is not present in Tragulidae and camels), located between the reticulum and abomasum. The mucous coat on the inner surface of the omasum, except for on the bottom, forms longitudinal folds of varying heights, or laminae that are similar to the pages of a book (hence the Russian name knizhka, literally “book”). These laminae are mobile, since they have smooth muscle. Thus, the cavity of the omasum is divided into narrow chambers and only at its base, which the free ends of the laminae do not reach, is there an integral cavity, the canal of the omasum. In the omasum the feed that has been swallowed again by the animal after rumination is finally ground down and converted into a gruel-like substance that passes into the abomasum. Along the bottom of the omasum there is an abomasal groove, the sulcus omasi, serving as a direct continuation of the reticular groove; liquified food can flow along it directly into the abomasum.

References in periodicals archive ?
Liquid flow from the rumen and small intestine was determined using LiCoEDTA as a marker; whereas soluble non-ammonia N (SNAN) entering the omasum was fractionated into microbial and non-microbial N (defined as dietary N) using 15 N.
5 kg weight inserted into the abomasum two secure the sampling device in the omasum.
toxin in feed papilla and 1998a (calves) omasum ulceration 3-5 ppm (dairy Reduced IgA , Korosteleva et cow) serum albumin al.
Intake, rumen fermentation and nutrient flow to the omasum in beef cattle fed grass silage fortified with sucrose and/or supplemented with concentrate.
A rise in concentrations of SNAN in the omasum by increasing CP level with protein supplements has been reported using skimmed milk powder, wet distiller's solubles and rapeseed meal (Choi et al.
They also determined SGLT1 expression in several tissues and found high amounts in the stomach tissues, rumen and omasum, as well as in the intestinal tissues, the duodenum, jejunum and ileum.
Furthermore, compared with sheep, cattle have a relatively greater omasum and a smaller large intestine (McLeod and Baldwin, 2000; Hata et al.
Heart, lungs, spleen, rumen, reticulum, omasum, abomasum, small intestine, kidney and sexual organ weights were the heaviest in CBK followed by BCBK and JNC (Table 4).