View source for Cud

{{about|the digestive process of a ruminant|other uses}}
{{Refimprove|date=January 2017}}
{{Short description|Food regurgitated so it can be chewed further}}
'''Cud''' is a portion of food that returns from a [[ruminant]]'s stomach to the mouth to be chewed for the second time. More precisely, it is a [[Bolus (digestion)|bolus]] of semi-degraded food [[regurgitation (digestion)|regurgitated]] from the [[reticulorumen]] of a [[ruminant]]. Cud is produced during the physical digestive process of rumination.<ref>{{cite web|title=Ruminant Digestive System|url=http://faculty.fortlewis.edu/LASHELL_B/Nutr2-Rumdigestion.pdf}}</ref>

== Rumination ==
{{unreferencedsect|date=April 2023}} 
[[File:Water buffalo chewing cud - 01.ogv|thumbnail|A [[water buffalo]] chewing cud]]
The [[alimentary canal]] of ruminants, such as [[cattle]], [[giraffe]]s, [[goat]]s, [[Ovis|sheep]], [[alpaca]]s, and [[antelope]], are unable to produce the [[enzymes]] required to break down the [[cellulose]] and [[hemicellulose]] of plant matter.<ref>{{Cite journal |last1=Sansone |first1=Randy A. |last2=Sansone |first2=Lori A. |date=2012 |title=Rumination |journal=Innovations in Clinical Neuroscience |volume=9 |issue=2 |pages=29–34 |issn=2158-8333 |pmc=3312901 |pmid=22468242}}</ref> Accordingly, these animals rely on a [[symbiotic]] relationship with a wide range of [[microbes]], which largely reside in the [[reticulorumen]], and which are able to synthesize the requisite enzymes. The reticulorumen thus hosts a microbial fermentation which yields products (mainly [[volatile fatty acids]] and microbial protein), which the ruminant is able to digest and absorb. This allows the animals to extract nutritional value from cellulose which is usually undigested.

The process of rumination is stimulated by the presence of [[roughage]] in the upper part of the [[reticulorumen]]. The chest cavity is stretched, forming a vacuum in the gullet that sucks the semi-liquid stomach content into the [[esophagus]]. From the esophagus it is taken back to the mouth with retro [[peristalsis|peristaltic]] movements. When the stomach content, or the cud, arrives in the mouth of the ruminant, it is pushed against the palate with the tongue to remove excess liquid, the latter is swallowed and the solid material is chewed thoroughly so the cattle can extract the minerals present in the cud brought to the surface during rumination. The function of rumination is that food is physically refined to expose more surface area for bacteria working in the reticulorumen, as well as stimulation of [[saliva]] secretion to [[Buffer solution|buffer]] the rumen [[pH]].

When food has been degraded sufficiently it passes from the reticulorumen through the reticulomasal orifice to the [[omasum]] followed by the [[abomasum]] to continue the digestion process in the lower parts of the alimentary canal. No enzymes are secreted in the rumen. Enzymes and [[hydrochloric acid]] are only secreted from the [[abomasum]] (fourth stomach) onwards, and ruminants function from that point onwards much like monogastric animals, such as [[pig|pigs]] and humans.

== Chemistry ==
{{singlesource|section|date=April 2023}} 
The reticulorumen has an optimum pH of 6.5 for the microbe population to thrive. Consumption by ruminants of an insufficiently fibrous diet leads to little cud formation and therefore lowered amounts of saliva production. This in turn is associated with rumen [[acidosis]], where the rumen pH can fall to 5 or lower. Rumen acidosis is associated with a lowered appetite which leads to still lower rates of saliva secretion. Eventually, a collapse of the microbial [[ecosystem]] in the rumen will occur because of the low pH. Acute rumen acidosis can lead to death of the animal, and will occur if the animal is allowed to eat a diet with no roughage but high levels of highly [[digestible]] starchy concentrate. Some dairy cows in intensive systems of milk production may have sub-acute acidosis because of the high rates of cereals in their diets relative to an insufficient amount of forage. However, most producers provide adequate [[fodder]] in the form of [[hay]] to prevent this.<ref>{{Cite web|url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/rumination.html|title = Rumen Physiology and Rumination}}</ref>{{additional citation needed|date=April 2023}}

== Jewish dietary laws ==
[[Jewish dietary law|Jewish dietary laws]] state that an animal that chews the cud and has a [[cloven hoof]] is acceptable for consumption. Any animal that doesn't chew the cud and has a [[cloven hoof]] is unclean.

== Cuisine ==
Goat cud is sometimes an ingredient in [[Pinapaitan]].

== See also ==
* [[Chymus]]
* [[Cecotrope]]

==References==
{{reflist}}

[[Category:Digestive system]]
[[Category:Articles containing video clips]]
[[Category:Ruminants]]