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(vertebrate zoology)
The first chamber of the ruminant stomach. Also known as paunch.



(also paunch), the first and largest section of the four-chambered stomach of ruminants. The rumen occupies almost the entire left half of the abdominal cavity. In adult animals its volume equals four-fifths the volume of the entire stomach. In newborns, which are fed only milk, the rumen is half the size of the abomasum. The first section of the rumen is connected to the reticulum and the esophagus. The rumen’s walls consist of the serous membrane (exterior membrane), the muscular membrane (middle membrane), and the mucous membrane (interior membrane). The interior wall has bands that divide the rumen into sacs, which slow down the movement of food. The interior epithelial surface, except for the bands, has processes, or papillae. In camels and llamas the walls of the rumen have deep cells, in the floors of which open cardiac glands. Such glands are absent in the rumens of other ruminants.

Decomposition of plant substances through bacterial and protozoan activity occurs in the rumen. Volatile acids are assimilated through the surface of the mucous membrane. The food is subjected to the action of enzymes and is mixed. From the rumen the food enters the reticulum or is regurgitated into the mouth, where it is masticated again. The food then passes into the omasum through the esophageal groove.

T. B. SABLINA [22–10101]

References in periodicals archive ?
Bu calisma, kuzularda, rasyona farkli duzeylerde katilan kekik (Origanum vulgare) ucucu yaginin rumen fermantasyon parametreleri uzerine etkilerini saptamak amaci ile yurutulmustur.
The study evaluated the effect of three sample amounts (0.6, 1.3 and 2.6g of DM 100[mL.sup.-1] of rumen fluid) incubated in rumen fluid buffered (BRF-buffered rumen fluid) or not (PRF-pure rumen fluid) on total gas volume (TV), C[H.sub.4] production, dry matter degradation (DM Deg) and final pH after 24 hours in vitro incubation at 39[degrees]C.
As efficient as this can be, there is still a requirement for nutrients that bypass the rumen. A cow's requirement for bypass protein increases as her milk yield increases.
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Research demonstrated that rumen protected ARG and NCG supplementation has beneficial effect on mammalian reproduction, which are associated with complex metabolic networks [14] and improve the maternal-fetal- placental anti-oxidation capability, and promote fetal and placental development during early-to-late gestation when offered to underfed ewes [15].
It was then infused with [O.sub.2]-free C[O.sub.2] gas, and, simultaneously, strained rumen fluid was added as a microbial suspension (5%, v/v) using a syringe.
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El rumiante tiene escasez cronica de glucosa debido a que la mayor parte de la glucosa proveniente de la degradacion de los carbohidratos del alimento es fermentada en el rumen. Por lo tanto, el propionato se destina principalmente para la gluconeogenesis en el higado (Cook y Miller, 1953).
The aim of experiment was to determine the influence of dietary SRU and/or two different NSC sources on digestibility in general and rumen N utilization in particular in sheep and goats fed low quality forage.
001/2008.Three Jersey and one Nellore nonlactating and nonpregnant cows were surgically adapted with rumen cannula (10.2 cm diameter) and randomly allocated in a cross-over design, with 18-d periods.
Maintaining the optimal pH of the rumen requires that diets contain adequate amounts of physically effective fibre.