Rumen stomach and function

how many stomachs does a ruminant have?

• one stomach with four compartments

• 3 forestomachs and 1 true stomach

are forestamachs glandular?

no, they are non-glandular

what is considered the true stomach?

the abomasum

how does ingesta enter the rumen?

through the esophageal sphincter

rumen

• LARGEST compartment

• digestion happens through fermentation

what performs fermentation in the rumen?

microbes which take cellulose and breaks it down

types of microbes that perform fermentation in rumen

• bacteria

• protozoa

• fungi

what do the microbes break down cellulose into?

• convert cellulose—>simple carbohydrates—>volatile fatty acids (VFAs)

• convert proteins—>peptides and amino acids

3 types of VFAs produced

• propionic acid

• butyric acid

• acetic acid

volatile fatty acids

• absorbed across rumen wall

• transported to liver

what is propionic acid converted to in the liver?

glucose

what are butyric acid and propionic acid used for?

energy in tissues

how are materials distributed in the rumen?

• according to particle size and density

• fibrous material that has just been ingested floats on top of liquid layer close to esophagus

• small dense particles fall to bottom (grain and well-chewed particles)

rumination

• recently digested fibrous material is close to the esophagus and is regurgitated as cud

• cud is chewed further and then re-swallowed

how does mixing in the rumen occur?

through muscular contractions

reticulum

• located between rumen and heart

• where fermentation occurs

• honeycomb appearance

what does the honeycomb structure of the reticulum do?

increases the surface area

hardware disease

• heavy items that are digested go to reticulum which is close to the heart

• objects can pierce wall of reticulum and go into the pericardium causing an infection/abscess around the heart

omasum

• muscular and filled with leaf-like folds

• where ingesta travels to from the rumen

functions of leaf-like folds in omasum

• breaks down particulate matter further

• continues to absorb VFAs

• allows absorption of large quantities of H2O

abomasum

• true stomach

• highly acidic (pH~2)

• rugal folds like monogastric stomach

• contents flow through pylorus into small intestine

esophageal groove

• fold of tissue between esophagus and omasum

• transports milk directly into omasum to be digested in abomasum and small intestine