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Equine biology > Gastrointestinal tract > Flashcards

Gastrointestinal tract Flashcards

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1
Q

key features of equine digestion

A
  • non-ruminant herbivore with significant fermentation in hind gut
  • rely on microbes in GIT to break down fibrous portion of diet
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2
Q

development

A 
underdeveloped large intestine at birth
-increases over first year
foals begin suckling at 1-2 hours after birth and spend 6-8% of day suclkking
-by 8 weeks 2% of days
-21 weeks 50% of day eating solids
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3
Q

coprophagy

A
  • consumption of feces, common in horses

- possibly helps colonization of GIT

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4
Q

stomach

A

relatively small in horses and rarely empty

  • 2x capacity of pig
  • limited ability to vomit
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5
Q

transit times total

A

total 23-48 hours, 75% of time spent in hindgut’s cecum and colon

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6
Q

transit time stomach

A
  • fast through stomach: 2-6 hours following ingestion, about 75% liquid and 24% dry passed out of stomach
  • transit through stomach only 30 min to 1.5 hours
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7
Q

stomach digestion

A
  • carbs, proteins, and fats mix with digestive enzymes and partially digested when passed to small intestine’s duodenum
  • few microbes suited for acidic environment of stomach, but there are some anaerobic bacteria to help digest ready carbs
  • as digesta approaches stomachpH falls, due to HCl secretion that initiates pepsin activity and reducing fermentatio
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8
Q

small intestine anatomy

A

duodenum, jejunum, and ileum

  • total length 25 m
  • attached to mesentery and mostly freely mobile
  • where major digestion of proteins, fats, and non-structural carbs
  • enzymes produced by pancreas enter duodenum
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9
Q

large intestine/hindgut anatomy and function

A

cecnum and large colon

  • digesta reaches cecum by 30-45 minutes after leaving stomach
  • insoluble carbs pass through small intestine and are fermented by microbes in cecum and colon
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10
Q

hindgut environment/microbes

A

major microbes include cellulolytic proteolytic, lactate-using, and glycolytic bacteria

  • cecum more cellulotytic bacteria and less starch-using bac than colon as it is primary location of FIBER digestion
  • horses LESS EFFICIENT than ruminants but donkeys are similar to rums
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11
Q

hindgut shape and function of delaying digesta passage

A

long feeding times maintain full stomach and continuous supply of nutrients to host and microbes
-increased retention times are associated with increased digestibility, aided by delay of rate of passage through sacculation, large volume, and pelvic flexure

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12
Q

selective areas of retention

A

pelvic flexure, diaphragmatic flexure, sternal flexure and colonic separation mechanism of GIT
-contractions and anatomy result in physical separation of courser particles from finer ones and fluid retention

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13
Q

pelvic flexure

A

-retains coarse particles (1 cm or more) in CECUM and ventral colon, while fine and liquids move to left and right dorsal colon

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14
Q

colonic separation mech of GIT

A

-fluid retained in right dorsal colon, contractions in muscular wall of colon results in fecal ball production and absorption of fluid

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15
Q

2 types of carbs digested

A

non-structural carbs (sugars) and structural carbs=fibers

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16
Q

non-structural carbs

A
  • monosaccharides like glucose can be absorbed across the wall
  • sugars are hydrolyzed in small intestine by pancreatic a-AMYLASE
17
Q

structural carbs

A
  • hemicellulose, cellulose, lignin and pectin
  • made up of monosaccs joined by beta bonds that horses cannot break down
  • rely on microbes in hindgut to produce enzymes that break this fiber into useable components
18
Q

fermentation

A
  • volatile fatty acids VFAs are byproducts and can be used as energy source for horse
  • VFA produced from cellulose metabolized by microbes
  • microbes proteins contribute minimally to horse nutrition
19
Q

VFAs

A

> 50% of daily energy comes from them for horses

  • include acetic, propionic, and butyric acids
  • 7% of glucose production
20
Q

excess of non-structural CHOs

A
  • digestive capacity of small intestine can be exceeded when fed lots of cereal grains
  • grasses=3.5% starch vs oats 44% starch
  • recommendation: do not exceed 4g starch/kg BW/meal
  • excess non-structural carbs result in large portion of undigested material entering colon
21
Q

what happens when high starch content in stomach

A

-fermentation causes increaesed LACTIC ACID production, decreasing pH, disrupting microflora, and decreasing activity of FIBER-digestion

22
Q

illness caused by excess starch

A
  • lactic acidosis associated with laminitis
  • colic
  • diarrhea
  • stereotypies like crib-biting and pacing
  • reduced gut health
  • rule of thumb: change diet over 5 day period
23
Q

proteins

A

digested in small intestine

-protein of cells walls used as nutrition for microbes

24
Q

liver

A
  • metabolizes carbs, proteins, and fats
  • breaks down and excretes potential toxins
  • large storage capacity, esp for glucose
25
Q

liver anatomy

A
  • most cranial part is behind diaphragm
  • divided into lobes
  • NO GALL BLADDER
  • continuous flow of bile enters duodenum
  • most products of digestion pass through liver via portal vein
26
Q

glucose metabolism

A
  • liver maintains blood glucose in response to pancreatic hormones insulin and glucagon
  • after meal excess glucose undergoes glycogenesis, converted into glycogen for storage
  • glucose not stored is used to produce energy via glycolysis
27
Q

glucose metabolism between meals

A
  • blood glucose falls, liver responds via
    a) glycogenolysis, converting glycogen into glucose
    b) gluconegenesis, non-sugars like amino acids are converted into glucose
28
Q

fat metabolism

A
  • bile enters duodenum EMULSIFYING fats into smaller globules, which are broken down further by lipase enzymes
  • when excess: LIPOGENESIS where fatty acids and glycerol and stored in subcutaneous tissue
  • low energy: lipolysis in fat store cells convert back to glycerol and fatty acids, brought to liver
29
Q

protein metabolism

A

-AA transported to liver
excess=
a)aa converted into fat and stored in fat depots
b) made into glucose for energy via gluconeogenesis
DEAMINATION=amino group excreated as urine

30
Q

storage of vitamins and minerals

A

stored via hepatocytes

31
Q

bile

A
  • emulsifies fat
  • metabolic wastes and drug products may form part of bile which are then excreted from body with faeces
  • bilirubin, toxic end product of haemoglobin breakdown is removed via bile

Equine biology (16 decks)

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