ruminant
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White-tailed deer ( Odocoileus virginianus ) |
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| Ruminantia | ||||||||||||
| Scopoli , 1777 | ||||||||||||
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Ruminants (Ruminantia) are a subordination of cloven (Artiodactyla). They are herbivores and have a multi-part ruminant stomach which, through microbial digestion, enables them to use as food those carbohydrates that are indigestible for other mammals with only one stomach ( monogastric ) ( e.g. cellulose ). Ruminants are divided into the two groups of stag piglets and forehead weapon bearers .
In addition to ruminants, other herbivores such as kangaroos , slipper monkeys , horses and rabbits are able to digest cellulose with the help of microorganisms, but in the large intestine, which makes a further passage through the digestive tract necessary for the rabbits for the usability of microbial protein ( Caecotrophy ).
The term 'ruminant' comes from the fact that the pre-digested food pulp is choked up and chewed again when the animal is resting, before the mechanically further chopped food is swallowed again and fed to the actual digestion .
The senses of the ruminants are very pronounced due to the need for permanent enemy avoidance, ie they see, smell, taste and hear very well. Ruminants can be active both day and night. However, since their food predominantly grows outside of dense woodlands, i.e. in more open parts of the landscape and because their visual sense gives them an advantage in avoiding enemies during the day, they tend to be more active during the day. Where they are more frequently disturbed during the day, however, they increasingly shift their activities into the night.
Structure of the stomach
The gastric tract of ruminants usually consists of four sections: The abomasum (abomasum) corresponds to the single-cavity stomach of monogastric animals . Upstream there are three foregomas, which are differently differentiated sections of the esophagus : rumen (villi, rumen), reticulum (hood, reticulum) and leaf stomach (psaltery, book, book stomach, folded stomach, calendar, remover or omasus). The rumen, in turn, has an atrium, which is also known as the gizzard . This can also be counted separately, which increases the number of pre-stomachs to four or that of stomachs to five. Occasionally the rumen and reticulum are functionally combined to form the reticulorumen .
When grazing, the plant food is only roughly chewed and swallowed. It then gets into the rumen via the gizzard. In the rumen , but also in the other rumen, numerous microorganisms such as live bacteria , protozoa and yeasts with which the food pulp is mixed well. The microorganisms are able to break down most of the carbohydrates into substances that can be absorbed by the rumen wall. During this process, called ' fermentation ', carbohydrates that are indigestible for other animal species ( e.g. cellulose ) are broken down so that the ruminants can absorb them and use them for energy. The gases released during fermentation (especially carbon dioxide and methane ) collect in the dorsal rumen sac until they are released into the environment through burping, the trunk . The amino acid biosynthesis of the microorganisms is stimulated by urea , which is excreted in the saliva or the rumen or also fed to the diet, so that ruminants can do without any added amino acids.
The food pulp is now moved back and forth between the rumen and reticulum for further comminution and mixing, before it is transported back into the oral cavity in small portions by contractions of the reticulum and the centrifugal stomach as well as by backward-running peristaltic waves from the rest of the esophagus. The food is chewed even more finely by further chewing (rumination) before it is swallowed again.
The reticulate stomach performs a “sorting function”, which holds back large and coarsely chopped food components and transports small particles further into the leaf stomach . There, the food pulp is pressed out by contraction between the leaves and the water is absorbed, which thickens the food pulp and ensures that the digestive secretions are less diluted in the subsequent abomasum . Finally, the food pulp is transported into the abomasum , where - as in the case of monogastric animals - the pH value is lowered by secretion of hydrochloric acid and digestion , especially of proteins and fats, is carried out by the body's own enzymes . There, proteins are also released from the microorganisms in the food pulp, which are absorbed in the adjacent small intestine .
Due to the long time the food stays in the ruminant stomach, which is constantly mixed and finally thickened, bezoar stones are often formed . These "stomach stones" are swallowed hair and plant fibers that clump together and stick together and finally become harder and harder.
The ruminant newborns do not yet have a functional ruminant stomach. The rumen only takes up around 25% of the entire stomach, the much larger part comprises the abomasum . The digestive system functions in a similar way to mammals with an uncharged stomach ( monogastric animals ). During this phase, the newborns are heavily dependent on breast milk . The settlement of the microorganisms in the rumen begins shortly after birth. The process of rumination is controlled by the change in diet and begins with the first consumption of solid food. A stronger growth of the rumen only begins afterwards. In cattle, this can start around the second or third week of life and last until the sixth month. This increases the volume of the rumen, which also increases the transport capacity of the nutrients. There are also changes in the metabolism and functional shifts in individual organs, such as the liver .
Systematics
The ruminants can be divided into two groups:
- The stag piglets (Tragulidae) are the most primitive group. They lack the leaf stomach.
- The forehead weapon bearers (Pecora) always have the four-chambered stomach described above. The characteristic that gives them their name is the forehead weapons that are mostly present in these animals. They can be divided into five families :
- Giraffes (Giraffidae)
- Musk deer (moschidae)
- Forked horns (Antilocapridae)
- Deer (Cervidae)
- Horned Bearers (Bovidae)
Animals with a similar digestive system
Independent of the ruminants, some other animal groups have also developed a chambered stomach that allows them to digest food in much the same way. These include camels , hippos , umbilical pigs , sloths , white monkeys and colobus monkeys and the kangaroos . The hoatzin (crested chicken) digests in a similar way to ruminants, but here the lower end of the esophagus and the goiter are transformed into fore-stomachs.
The whales are related to the hippos and inherited the chambered stomach from their land-living ancestors. However, their stomach does not function as a ruminant stomach because they feed on animal food. Gray whales , bowhead whales and minke whales use bacteria to the Chitinskelett digest of krill.
Web links
Individual evidence
- ↑ by Engelhardt, Breves, Physiology of Pets , 2nd edition.
- ↑ Research report from the University of Bonn: Influence of a negative RNB on milk yield (PDF).
- ↑ KL Anderson, TG Nagaraja, JL Morrill, TB Avery, SJ Galitzer and JE Boyer: Ruminal microbial development in conventionally or early weaned calves. Journal of Animal Science, 34, 1987, pp. 1215-1226
- ^ RL Baldwin, VI, KR McLeod, JL Klotz and RN Heitmann: Rumen Development, Intestinal Growth and Hepatic Metabolism In The Pre- and Postweaning Ruminant. Journal of Dairy Sciences 87 (E. Suppl.), 2004, pp. E55-E65
- ↑ K. Govil, DS Yadav, AK Patil, S. Nayak, RPS Baghel, PK Yadav, CD Malapure and D. Thakur: Feeding management for early rumen development in calves. Journal of Entomology and Zoology Studies 5 (3), 2017, pp. 1132–1139
- ↑ a b C. EDWARD STEVENS AND IAN D. HUME: Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients. Physiological Reviews Vol. 78 No. April 2, 1998, pp. 393-427 .