The digestive process of ruminants is complex and quite long since these mammals, including cows , are capable of eating and then “storing” said food until they ruminate, that is, the regurgitation of what they have ingested. . Let us then know in more detail what digestion is like and how it works in ruminants.
This is how digestion works in ruminants
Ruminants are an important group of placental mammals , more precisely a suborder of the order Artiodactyls (from the Greek artios pari and dactylos finger), which includes several large herbivores, such as cows, sheep, deer, antelope and giraffe.
Ruminants are characterized by having a very complex digestion, formed by three gastric compartments (rumen, reticulum, omasum) and a real stomach (abomasum). Digestion takes place in the abomasum and is preceded by microbial fermentation, which occurs in the aforementioned compartments. Precisely because of this peculiarity they are also identified as polygastric animals.
Ruminants can ingest a considerable amount of plant material, almost without chewing it, accumulating it in the first of the three pre-stomachs, the rumen. Here, by specific bacteria, molds and cellulolytic protozoa, a first demolition of plant fibers begins. A few hours after the primary ingestion, the rumination process takes place (reflex by which the animal regurgitates the highly fragmented plant material in the oral cavity).
Rumination consists of four main phases:
- aspiration , plant material is aspirated from the rumen into the esophagus;
- expulsion , plant material is expelled from the esophagus into the oral cavity;
- chewing, the plant material is chewed slowly and carefully;
- swallowing , once the food is finely ground, it is swallowed again.
The role of rumination is fundamental, it allows to facilitate the maceration of the ingested food , the mixing of the content with the saliva, the grinding of it to facilitate its absorption, the uniform distribution of the cellulolytic microorganisms and the elimination of part of the anhydride, dioxide of carbon and methane derived from fermentation processes.
The second of the three pre-stomachs of ruminants is the reticulum (the smallest), it is made up of many reticular cells (square or hexagonal), which resemble the honeycomb in shape and structure, has an outlet in the esophagus and communicates widely with the rumen. This network plays a fundamental role in the fermentation and mixing of the material ingested during rumination, one of its main tasks is to separate the finest particles from the fermentation mass, which can continue towards the gastrointestinal tract.
The last of the three pre-stomachs is the omasum , which allows the passage of fermented plant material to the abomasum. Its main function is to reabsorb part of the liquid component of the fermented ingestion. The internal walls of the omasum have numerous folds (omasal sheets), which allow it to increase the absorbent surface.
In the abomasum (called “colloquially” true stomach) fermented ingestion is subject to the action of digestive processes (gastric juices), similar to what occurs in the stomach of monogastric animals (such as humans). The digested plant substances are released, through the pin, into the small intestine for the absorption phase.
The three pre-stomachs of ruminants are also called fermentation stomachs, while the glandular stomach of the abomasum, compared to the others, has an extremely acidic pH and the fermentative reactions of bacteria, protozoa and molds are disrupted.
In young animals, the prestomacal compartment is underdeveloped and non-functional. On the other hand, the milk-based diet does not require fermentation reactions. Therefore, there is an organ associated with the pre-stomachs, called the esophageal shower, which allows the transit of breast milk directly from the esophagus to the abomasum. This organ loses functionality with the growth of the animal, until it is completely atrophied in adult specimens (meanwhile, the first three stomachs have developed and have acquired full functionality).
