Rumen

Rumen the rumen is the first and the largest chamber of the four-chambered stomach system of ruminant animals. The ruminants can consume and digest fibrous feeds and non-fibrous ones. Most importantly, they can regurgitate (bringing back from the rumen) the ingested meals for chewing during rest time, called rumination. The rumen is the chamber where the ingested feeds enter first. It can hold 25 gallons or more of materials, depending on the animal's size.

The rumen comprises several muscular sacs, dorsal, ventral, cranial, etc., separated by longitudinal muscular pillars. The rumen is also provided with two layers of muscles; a superficial layer and a deep layer. These muscular pillars and layers increase the surface areas and thus increase more microbial digesting areas. The rumen contents are very heterogenous and include many semisolid digesta, solid materials, liquid, and gas. The rumen contents are in the periodical movement called the peristaltic movement, brought about by a series of muscular contractions. The rumen is inhabited by the most varied and dense microbial population, which is divided into 3 groups; bacteria, the protozoa, and the fungi. The approximate population of bacteria is 1010 consisting of 200 species, and protozoa 106, having 20 species per milliliter of rumen liquid, but these numbers are variable. Some bacteria are starch and soluble carbohydrate digesters, some are fiber digesters, and some are fat digesters. Almost all the microorganisms are strictly anaerobic (without oxygen). The rumen movement allows the feed particles remaining in every corner of the rumen to be digested. The digestion taking place in the rumen is solely by the microorganisms and is termed microbial fermentation, which produces a considerable amount of gas consisting of carbon dioxide and methane. The microbes adhere to feed particles and digest the feed through the secretion of the required specific enzymes from their body. The rumen is anaerobic and has a constant level of PH (6.2 – 7.0) and temperature (39 – 410C) that maintains an environment suitable for the survival of microbes and microbial digestion. [Md. Ali Akbar]