Comparative Digestive Systems

actions in digestion

mechanical, chemical, microbial

digestion

continuous process along alimentary canal, breaking down of food

alimentary canal

mouth, pharynx, esophagus, stomach, small intestine, large intestine

monogastric

one stomach, humans and pigs

modified monogastric

single stomach with specialized compartments that aid in digestion, horses and birds

ruminant

more than one stomach compartment, sheep cattle goats and llamas

monogastric diagram

ruminant diagram

specialized monogastric diagram

monogastric passage rate

8-12 hrs

ruminant passage rate

96-120 hrs, 6-8 hrs per day

salivary gland secretions

water, mucin, bicarbonate salts

mucin

lubrication aid for swallowing

bicarbonate salts

acts as a buffer to regulate stomach pH

swine mouth secretion

salivary amylase

ruminant mouth secretions

no enzymes

no ruminant mouth enzymes

provides source of N, P, and K

esophagus

ingested material moves via muscular contractions known as peristaltic waves

horse esophagus

only one way peristaltic waves

ruminant esophagus

two way peristaltic waves, allows chewing of cud

esophageal groove

prevents milk from entering the rumen of suckling animal by bypassing the reticulo-rumen and becoming fermented

reticulum volume

5%

rumen volume

80%

omasum volume

7-8%

abomasum volume

8-9%

reticulum

not completely separated from rumen, walls lined with intersecting ridges resembling a honeycomb

rumen

large, hollow, muscular compartment with papillae lining walls that secrete no enzymes and fills most of the left side of the abdominal cavity

rumen functions

storage, soaking, mixing, breakdown, fermentation chamber

fermentation chamber (rumen)

provides ideal environment for microbes to synthesize water soluble vitamins and vitamin K as well as deamination reactions

rumen provides bacteria

warm, moist, dark, anerobic conditions with 6.8 pH and substrate

bacteria provide rumen

VFAs, CP, vitamin K, B vitamins, body protein

Volatile fatty acids (VFAs)

three main energy sources in ruminant diet: propionate, acetate, butyrate, and horses and swine don’t use these well

proprionate

energy like glucose, higher in grain fed animals

Acetate

high in grazing animals

butyrate

VFA energy source with no change in concentration depending on feed

eructation

burping to prevent fatal bloat

urea cycle

takes nitrogen across the rumen wall back to the salivary glands in order to preserve nitrogen in the system

omasum (manyplies)

spherical organ filled with muscular laminae studded with short papillae

omasum functions

reduction of particle size and absorption of water

colostrum

milk produced up until 30 hrs after birth to provide nutrients and antibodies for developing the immune system

abomasum

essentially the same as the stomach in non-ruminants

monogastric features

pH around 2-3, stores ingested food, muscular movements cause physical breakdown, secretes digestive juices

digestive juices

gastrin, hydrochloric acid, pepsin, rennin

horse stomach

larger than other species, glandular plus non-glandular regions divided by margo plicatus, ulcers

gastrin

hormone that causes release of digestive enzymes

gastrin stimuli

stomach distension, presence of partially digested proteins, hypercalcemia

gastrin inhibitors

presence of acid in stomach, somatostatin

hydrochloric acid

activates pepsin, constitutes majority of gastric acid

parietal cells

secrete HCl

pepsinogens

proteolytic enzyme that begins protein digestion, degrades food proteins into peptides

chief cells

release pepsinogens

rennin

complex of enzymes produced in all mammals to digest milk

small intestine

duodenum, jejunum, ileum

Duodenum secretion providers

Brunner’s gland, pancreas

Brunner’s gland

Alkaline secretion for duodenum

Pancreas

Secretes majority of digestive juices with hormone secretin for duodenum

Enzyme for peptides

Peptidase

Enzyme for lactose

Lactase

Enzyme for sucrose

Sucrase

Enzyme for maltose

Maltase

Enzymes for protein

Chymotrypsin, trypsin

Enzyme for lipids

Lipase

Enzyme for carbohydrates

Amylase

Jejunum

Active site of nutrient absorption of AAs, sugar, fatty acids, glycerol with villi to increase absorptive area

Illeum

Second active site of nutrient absorption, mainly absorbing vitamin B12 and bile salts

Liver

Has bile salts and cholesterol

Bile salts

Emulsify fats, activate lipase, stored in the gall bladder

Large intestine parts

cecum, colon, rectum

large intestine function

microbial digestion of VFAs and MCPs, absorption of water, synthesis of B vitamins

Horse large intestine

60% of GIT

Horse cecum

bacterial fermentation, synthesis of water soluble vitamins and vitamin K, proteins considered of limited value to horse

health issues in the digestive system

founder, colic, acidosis, ketosis, milk fever, urinary calculi, thiamine deficiency

Lignin

undigestible plant fiber

old tall plant

high in lignin

bolus

ball of food that goes back and forth between rumen and mouth for remastication

rumen volume

40-50 gal

essential amino acids

A.A.s essential for life that must be ingested

lysine

essential AA for swine

CHONS

protein atoms

CHO 1:2:1

carbohydrate atoms

CHO not 1:2:1

lipid atoms

CHONPS

nucleic acid atoms

microbial crude protein

primary protein source for ruminants

copraphagy

animal with spiral colon that poops pellets and will eat shit to regain CP and B-vitamins

Founder cause

overload of carbonaceous concentrates (too many simple carbohydrates)

Horse cecum volume

25 qts

rennin

clot milk for digestion

Digestibility

how fast food moves through the GI tract

Urea

non-protean nitrogen source, makes up 1-3% of diet

founder

coffin bone points down as a consequence of severe laminitis from overfeeding

colic

twisted gut

urinary calculi

Ca:P ratio off

transfonation

move bacteria from one animal’s rumen to another