Equine Digestive Tract Anatomy: foregut Flashcards
how an animal is fed is dependent on…
first on what is available and the anatomy of the digestive system
horses flourished in america
because of the environment, they did not flourish in other countries because good feed wasn’t available and intestinal parasites were abundant
horses digestive system
long esophagus, small stomach (acidic), hindgut fermentation in the large and functional cecum
ruminant digestive system
foregut fermentation in rumen, leftover nutrients are absorbed in true stomach (abomasum)
human digestive system
hindgut fermentation, no functional cecum
pig digestive system
no functional cecum, hindgut fermentation, grain based diet
cellulose
50% carbon, structural carbohydrate, not available to mammalian enzymes
cellulase
bacterial enzyme necessary for the breakdown of cellulose (cellulytic bacteria)
efficiency of cellulose breakdown
dependent on size of fermentation vat
end product of fermentation
energy, short chain VFA
crainial fermentation
ruminants
caudal fermentation
horses
process and outcome of fermentation
identical in rumen and cecum
position of fermentation vat in relation to small intestine
important in animal’s physiology and digestion
horse
fermentation after small intestine
cow
fermentation before small intestine
digest cellulose
both ruminants and cecal digestors
directly utilize dietary hexose (glucose)
ruminants don’t, cecal digestors do
ruminant utilization of glucose
first utilized by bacteria, digest and absorb short chain fatty acids
cecal digestors utilization of glucose
mostly digested and absorbed in foregut
utilize microbial protein
ruminants can, cecal digestors can’t
ruminant utilization of microbial protein
microbial protein absorbed because fermentation is before the small intestine
cecal digestor utilization of microbial protein
microbial protein is excreted in feces, VFA absorbed in large intestine
microbial protein
ruminant microbes washed down through tract and digested and absorbed
horse digestive system classification
non-ruminant herbivore or monogastric with a functional cecum
efficiency of fermentation vat
dependent on the size of the vat
why don’t horses have a rumen?
they would be less athletic, rumen is large while the hindgut system is smaller
horse digestive anatomy: mouth
mastication and saliva production
horse saliva production
5-10 liters per day
saliva is produced with chewing
more chewing equals more saliva
saliva function
aids in making soft bolus for swallowing and buffers stomach acid to prevent ulcers in stomach and esophagus
discreet feeding downfalls
less chewing causes less saliva and less buffering of the stomach, leading to ulcers, tonic gastrin leads to stomach ulcers
esophagus
contains cardiac valve that is functional, difficult to expel gas by eructation or vomitting
cardiac valve
can close off and cause gastric rupture, gastric distention, and colic
colic
general term for gastrointestinal distress and pain, commonly caused by hindgut
horse esophagus
smooth muscle decreased compared to cows, sheep, and dogs because horses don’t eructate
stomach
small, 10% of total tract, with a fast flow rate
gastric emptying
dependent of intake, rate of flow increases with volume, impacts digestive efficiency
two functional sphincters of the foregut-stomach
cardiac and pyloric
foregut-stomach glandular tissue
secretory function
hydrochloric acid
continuously secreted, acidic environment that kills bacteria
pepsinogen
converts to pepsin and breaks down peptides
gastrin
peptide continuously secreted and in response to gastric distention secreted from gastrin cells in stomach mucosa, stimulates secretion of HCl and protein synthesis in the stomach and duodenum
gastrin
continuously excreted because horses are always eating, gastrin is released in response to presence of food in stomach and causes release of gastric acid leading to the low pH of the stomach
what is buffering the stomach?
saliva from chewing, more saliva leads to a higher buffering capacity
foregut-small intestine parts
duodenum (1 m), jejunum (25 m), ileum (0.5 m)
foregut-small intestine similar function
similar function to other monogastric and ruminant animals
small intestine function
digestion and absorption of protein (amino acids), carbohydrates (monosaccharides), fats (fatty acids), vitamins and minerals
fats in horses
important for equine diet, able to feed more fat and not influence fermentation
fat in ruminants
fat decreases fermentation in ruminants
small intestine rate of passage
quick, 5 hour on average for solids, liquids pass to the hindgut faster
rate of passage intake
increased intake increases rate of passage
rate of passage feed
affected by physical form of feed, pelleted rations pass quicker than long-stem forage
