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ANSC 464 - Companion Animal Nutrition > Lecture 1b - Digestive Physiology of Horses > Flashcards

Lecture 1b - Digestive Physiology of Horses Flashcards

1
Q

Why would horses have such a large LI?

A
  • energy metabolism; they have to extract sufficient energy from plant material
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2
Q

What does the LI of a horse include?

A

Caecum, ascending, and descending colon

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3
Q

Horses are obligate…

A

Obligate Hindgut Fermenters

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4
Q

What part of the LI is in place for fiber fermentation?

A

Large caecum

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5
Q

What macronutrient are horses best adapted for to utilize?

A

FIBER!!!
- they have a very large caecum for fiber fermentation

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6
Q

What are 6 reasons for colic?

A

Gas
Obstruction
Strangulation
Impaction
Inflammation
Ulceration

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7
Q

What is saliva secretion stimulated by?

A

Mastication

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8
Q

Why does horse saliva contain a small concentration of bicarbonate?

A
  • provides buffer against stomach acids
  • allows some microbial fermentation in stomach
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9
Q

What 2 adaptations allow horses to increase chewing intensity?

A
  1. mastication
  2. large # of molars
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10
Q

What are the 3 regions of the stomach and their corresponding epitheliums?

A

Oesophageal region
- Squamous epithelium

Fundic region
- Glandular epithelium (ability to secrete)

Pyloric region
- Glandular epithelium

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11
Q

In what regions of the stomach can microbial fermentation occur?

A

oesophageal and fundic regions

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12
Q

What is secreted in the Fundic region vs the Pyloric region of the stomach?

A

Fundic
- parietal cells = HCl
- Zymogen cells = pepsin

Pyloric
- gastrin (which increases HCl and pepsin secretion)

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13
Q

Can horses vomit?

A

NO! Strong sphincter at top of stomach prevents vomiting

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14
Q

How does the horses stomach compare to dogs and cats?

A

Horse
- The stomach is a small organ in an adult horse. Digesta passes quickly into the SI with a relative emptying time of 120 min.

Dogs/Cats
- Longer emptying time

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15
Q

How may short gastric emptying time (120 min) relate to feeding behaviour?

A

Encourages constant grazing and constant meals to ensure digesta flow continues and there is access to energy

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16
Q

What are the 3 parts of the SI?

A
  1. Duodenum (~3m)
  2. Jejunum (~20m)
  3. Ileum (~45 cm)
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17
Q

What is the SI the primary site of digestion and absorption of?

A

protein, starch and fat

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18
Q

What is the exocrine functions of the pancreas? What enzymes play a role?

A
  • Secretes enzymes and bicarbonate salts into the gut
  • Enzymes: inactive proteases, lipases and amylases
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19
Q

What is the endocrine fxn of the pancreas?

A

Secrete hormones into the blood
- insulin, glucagon

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20
Q

What is the role of insulin?

A

Anabolic hormone making sure absorbed nutrients entering the portal vein are properly stored in tissue

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21
Q

What is bile produced by?

A

Liver

22
Q

What is unique about the horse in terms of bile?

A

No gall bladder to store it in!
- bile continuously drains into SI

23
Q

What does bile do?

A

Emulsify dietary fat and activate enzymes to aid in fat digestion

24
Q

Why the adaptive feature of missing a gall bladder?

A

Diet of horse is low in fat so there may not be a reason to store large quantities of bile. Secondly, horses have continual flow of digesta so they need continual release of bile.

25
Q

What is at the start of the LI?

A

Caecum
- very large
- 1 m long; 25-35 L capacity

26
Q

What does the Caecum contain? What is it responsible for?

A

Contains microbial population (protozoa, bacteria, and other microorganisms) to breakdown fiber

Responsible for microbial synthesis of SCFA and protein

27
Q

What are the 4 large compartments and 3 major flexures of the large colon (middle of the LI)?

A
  1. Right ventral colon
    - sternal flexure
  2. Left ventral colon
    - pelvic flexure
  3. Left dorsal colon
    - diaphragmatic flexure
  4. Right dorsal colon
28
Q

What is the difference between the SI and LI?

A

SI
- villus
- crypt

LI
- NO villi
- crypts are deeper compared to SI

29
Q

What are 4 ways the intestine increases capacity?

A
  1. coils
  2. folds
  3. villi
  4. microvilli
30
Q

What are the several categories of aa relative to how they are absorbed via the epithelial cells?

A

Polar or Nonpolar
Acidic or Basic or Neutral `

31
Q

Why are AA characteristics important for GI physiology?

A

Depending on the category of AA they will have to deal with unique transporters to be absorbed and it might mean there is competition between AA to be absorbed

32
Q

What is the difference between exoproteases and endoproteases?

A

Bonds on the far left or right of the polypeptide chain are cleaved by exoproteins.

Bonds within the peptide chain are cleaved by endoproteases

33
Q

Where is Pepsin located and what does it do?

A

Location: Stomach

Action: cleaves bonds of aromatic AA at the N-terminus

34
Q

What are the 4 enzymes that aid in protein digestion from the pancreas?

A
  1. Trypsin
    - cleaves peptide bonds joining basic AA
  2. Chymotrypsin
    - cleaves peptide bonds containing uncharged AA
  3. Elastase
    - cleaves peptide bonds next to small AA
  4. Carboxypeptidase
    - cleaves carboxy-terminal peptide bonds; liberates single AA
35
Q

What are the 3 enzymes involved in protein digestion and absorption from the intestine?

A
  1. Aminopeptidases
    - cleaves peptide bonds next to N-terminal AA oligopeptides; releases single AA or 3-6 AA peptides
  2. Dipeptidases
    - various specificity; cleaves dipeptides into free AA
  3. Tripeptidases
    - various specificity; cleaves tripeptides into free AA + dipeptide
36
Q

What might be reasons for AA absorption to happen as single AA and small peptides?

A

Energy preservation!

37
Q

Why is brush border transport of proteins not limited in some young mammals?

A

To transfer maternal immunity (antibodies)
- proteins and polypeptides are able to cross the brush border

38
Q

What form of AA are entering portal circulation?

A

Mainly free AA

39
Q

What type of transport is required for most AA?

A

Active transport!

40
Q

What is required for active transport?

A

ENERGY

41
Q

What enzyme from the pancreas is involved in CHO digestion and absorption?

A

alpha-amylase
- hydrolyzes starch to alpha-limit dextrins (shorter chains of glucose)

42
Q

What 4 enzymes from the intestine are involved in CHO digestion and absorption?

A
  1. Glucoamylase
    - hydrolyzes alpha-limit dextrins to single glucose units
  2. Maltase
    - cleaves maltose into single glucose units
  3. Isomaltase
    - hydrolyzes short chain glucose units to single glucose units
  4. Sucrase
    - cleaves sucrose into fructose and glucose
43
Q

What is the general name of cells that produce incretins?

A

Enteroendocrine cells

44
Q

What enzyme is linked to fat digestion and absorption?

A

Lipase
- location: pancreas
- primary action: break down triglycerides into free fatty acids and monoglycerides

45
Q

Where do absorbed fats drain into first?

A

The lymph vessel

46
Q

Where do SCFA produced by fermentation drain into?

A

LCFA absorbed into SI into lymph

SCFA can be taken up via a transport mechanism in the SI or LI

47
Q

What is the major site of SCFA production and absorption?

A

LI

48
Q

What are the 3 main SCFA?

A

acetate, propionate, butyrate

49
Q

What are the 3 modes of uptake for SCFA?

A
  1. passive
  2. facilitated
  3. symporter
50
Q

Which companion animal can adapt more quickly to a change in diet?

A

dog (bc they are omnivores)

ANSC 464 - Companion Animal Nutrition (20 decks)

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