parts of digestive tract

Question 1

mouth considerations

Answer 1

dentition-ageof horse foal vs mature vs aged horse, dental injuries, throat, tongue

Question 2

Mouth function

Answer 2

chewing=salivation, lubricant and buffer

Question 3

stomach

Answer 3

relatively small, inelastic, susceptible to gastric rupture, no vomiting, acid secretion is continuous

Question 4

food mat

Answer 4

layer of feed that divides the non-glandular and glandular regions of the stomach

Question 5

small intestine

Answer 5

starch digestion is variable, high amount of starch= decreased digestibility, source of starch (oats, corn, barley) are all different, processing of starch makes it more easily digestible, whole grains=decreased digestibility
fat is digested fairly efficiently in the SI
protein digestion is variable, protein in seeds+grains=increased digestibility, proteins in forage=less digestible

Question 6

large intestine

Answer 6

microbial community-bacteria, protozoa, viruses (fungal community), individuals have different roles, horses and microbes live in symbiosis (horses provide habitat, microbes play nutritional role and pathogen protection), LI acts as a reservoir for H2O and electrolytes (2-3 lb H2O/lb of dry matter)

Question 7

digestion og carbs in the upper gut

Answer 7

alpha-amylase is secreted from the pancreas and turns starch molecules into dissachardies, the disaccharides then bind with amylase in the wall of the small intestine to catalyze the reactions that break the disaccharides into single glucose molecule

Question 8

fate of glucose absorbed in the upper gut

Answer 8

absorbed through the intestinal wall and ends up in the blood capillary network surrounding the intestine. in the blood vessels, the glucose is transported to tissues for immediate use (energy, ATP), converted to fat or storage as glycogen

Question 9

protein digestion in the upper gut

Answer 9

begins in the stomach with the enzyme pepsin to break down protein into smaller molecules. the pancreas secretes pepsin and trypsin into the small intestine to break down peptides into amino acids

Question 10

fate of amino acids absorbed in the upper gut

Answer 10

amino acids are carried through the blood to the tissue to build proteins for building tissues, hormones, components of enzymes and antibodies, or stored as fats (CHO), nitrogen is excreted in the urine

Question 11

Digestion of lipids in the upper gut

Answer 11

fats are not H2O soluble. bile from the liver is continuously secreted into the small intestine. bile salts surround and emulsify the fat so it can be enzymatically digested by lipase from the pancreas. the lipid products combine with bile acids to form micells

Question 12

fate of lipids absorbed from the upper gut

Answer 12

absorbed by cells of the intestinal lining and repackage with cholesterol and proteins into chylomicrons. too big to be absorbed into blood capillaries so they are taken up by intestinal lymphatic cells once they enter the lymphatic system, the lipids enter the blood stream throughout the thoracic duct where they can be used as fuel or stored as fat, cell membranes or other compounds

Question 13

digestion of fiber in the hind gut

Answer 13

occurs in the cecum that contains microbes producing the enzymes to break the glucose and fiber bonds. excess starch and sugar are also fermented in the large intestine resulting in VFAs.

Question 14

fate of products from fiber digestion

Answer 14

VFAs are absorbed through the intestinal wall. propionate is used as energy, fat synthesis and glucose production, acetate is used for energy and fat synthesis and butyrate is like acetate, but there is much less so less important undigested fiber ends up as feces

Question 15

fate of protein in the hind gut

Answer 15

protein digestion does not result in amino acids but carbon and nitrogen strands may be used in the body as nonessential amino acids, secreted out as ammonia or used as microbial protein

Question 16

fate of starch reaching the hind gut

Answer 16

the starch results in VFAs and propionic acid that may be converted back to glucose in the liver

Question 17

nutritional role of microbes

Answer 17

digest fiber=VFAs (acetate-C2, propionate-C3 and butyrate-C4), digests sugars and starches=VFAs (acetates=low, propionate=high can be converted to lactic acid, and butyrate=intermediate
microbes also digest protein to use themselves and liberate ammonia, have some B vitamin synthesis, microbial community is susceptible to changes in diet (adaptable, large, sudden changes may cause dysbiosis)

Question 18

pathogen role of microbes

Answer 18

colonization resistance, compete for substrate (food), produce compounds or change environment to decrease pathogens, produce a physical barrier at the GI lining, disturbances to normal community decrease pathogen defense, antibiotic associated diarrhea (ADD) or antibiotic associated colitis (inflammation of colon)