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ANSC 464 - Companion Animal Nutrition > Lecture 1a - Digestive Physiology of Dogs & Cats > Flashcards

Lecture 1a - Digestive Physiology of Dogs & Cats Flashcards

1
Q

What is the primary role of the digestive system?

A

Break down large food molecules into simple forms that can be absorbed by the body for use

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2
Q

Beyond breaking down food, what is another function of the GI tract?

A

Epithelial layer acts as a barrier; it functions to let things through but also keep things out (ex. bacteria)

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3
Q

What are 2 key clinical signs of the GI tract not working well?

A

Diarrhea and vomiting

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4
Q

Dogs and cats have a relatively similar GI tract except for what?

A

Length of the GI tract
- dog has a longer digestive tract, cat has a shorter digestive tract

Dog: BL = 0.75m, SI = 3.9m, LI = 0.6m
Cat: BL = 0.5m, SI = 1.7m, LI = 0.4m

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5
Q

What does intestinal length influence?

A

retention time of food in the gut; animals have a longer GI tract than their body bc it allows for more digestive and absorptive capacity

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6
Q

What are the structures used to increase digestive and absorptive capacity of the GI tract relative to body weight?

A
  1. Villi
  2. Microvilli
  3. Coils (of SI)
  4. Folds
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7
Q

Generally, what type of gastrointestinal system do dogs and cats have?

A

monogastric gastrointestinal system

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8
Q

What type of diet is a dog adapted to?

A

An omnivorous diet containing a high proportion of animal tissues

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9
Q

For what macronutrient(s) is the capacity to digest the lowest for a dog?

A

Fiber!
- for fiber you need microbes and the dog has smaller capacity of GI tract

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10
Q

What is the consequence for fermentation for the dog?

A

Limited capacity to ferment fiber bc it has a smaller SI in conjunction to body size unlike other species such as a pig

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11
Q

What type of diet is the cat adapted to?

A

A carnivorous diet

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12
Q

What stimulates the salivary glands to produce saliva?

A

smell and presence of food

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13
Q

What are the 4 pairs of salivary glands?

A
  1. parotid
  2. mandibular
  3. sublingual
  4. zygomatic
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14
Q

What affects saliva amount and composition?

A

Type of food ingested and its moisture content

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15
Q

What are the 3 roles of the mouth (oral cavity)?

A
  1. eat and ingest
  2. taste
  3. texture

*must think of both taste and texture when developing pet food

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16
Q

What does saliva aid with?

A
  • the mixing/chewing of food and lubrication before swallowing
    *many dogs and cats swallow their food with minimal chewing
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17
Q

Unlike people, what enzyme do dogs and cats lack in their saliva?

A

Alpha-amylase
= starch digestion not initiated

  • an implication could be that there is less glucose sensing in the mouth
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18
Q

For dogs, what is a very important fxn of saliva?

A

Evaporative cooling

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19
Q

What type of teeth do dogs have and what do they use them for?

A
  1. Canine teeth for ripping and tearing
  2. Large molars and premolars for grinding and chewing large or tough pieces of food
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20
Q

What are cats teeth best suited for?

A

Best suited for holding and killing small prey animals; less efficient in chewing and grinding food

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21
Q

What is a different between dog and cat teeth?

A

Dogs have some molars (for grinding and chewing) whereas cats barely have any

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22
Q

What does the cell-lining of the esophagus produce?

A

Mucus to help food passage

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23
Q

What is the use of peristalsis by the esophagus?

A

Peristalsis is used to move the food; it only takes a few seconds to reach the stomach

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24
Q

What is found at the base of the esophagus/top of stomach? What does it do?

A

Cardiac sphincter
- relaxation causes food to enter into the stomach
- immediately closes again to prevent the reflux of food from the stomach to the lower esophagus

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25
Q

What are the 4 functions of the stomach?

A
  1. Food reservoir
  2. Mixes food
  3. Regulates flow of digesta into the SI
  4. Initiates chemical digestion of protein; secretion of HCl and pepsinogen; no digestion of CHO and fats
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26
Q

Are CHOs and fats digested in the stomach?

A

no

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27
Q

What is unique to the stomach relative to the rest of the GI tract?

A

It’s very acidic pH (2-3)
- acidity causes break of disulfide bonds, starting to unravel the protein which can ONLY happen at an acidic pH

28
Q

What 2 sections is the stomach divided into? What section expands?

A
  1. Proximal section
    - expands during temporary food storage which allows dogs to eat discrete meals
  2. Distal section
29
Q

What is gastric secretion in the stomach influenced by?

A
  • Influenced by the amount of protein in the meal, the meal volume and hormones
30
Q

How is the rate of gastric emptying controlled?

A

Rate controlled via:
1. stomach volume
2. body wt
3. water intake
4. diet type
- high density particles empty slower than smaller sized particles

31
Q

What roles of soluble fibre?

A

Makes digest more sticky = takes longer for stomach to empty

32
Q

For what kind of animal would we want to reduce the rate of gastric emptying? How would we do this?

A

An animal with diabetes; if emptying is rapid there would be a big increase of glucose

Add soluble fiber to decrease the rate of glucose absorption by slowing the rate of gastric emptying

33
Q

How is the stomach different in a cat vs. dog?

A

Stomach as a storage reservoir is less important for cats than dogs
- Average half-emptying times are: 22-449 min for a cat vs 72-240 min for a dog

Stomach is simpler for cat than dogs bc animal protein is simpler to digest
- relatively smaller with smaller glandular fundus

34
Q

What is the small intestine the primary site of?

A

Primary site of chemical digestion and absorption of fat, starch, sugar, and protein

35
Q

What is the first thing that happens when acidic chyme moves from the stomach into the SI?

A
  • stimulates the secretion of pancreatic juice which increases pH of digesta; enzymes that work in the I have optimum pH closer to 7
  • chyme is mixed with enzymes in the duodenum that come from duodenal mucosa and pancreas
36
Q

What are the exocrine fxns of the pancreas?

A

Secretes enzymes and bicarbonate salts into gut to establish optimal pH
- enzymes: inactive proteases, lipases and amylases

37
Q

What are the endocrine fxns of the pancreas?

A

secrete hormones into blood

38
Q

What is unique about the pancreatic juices of a dog?

A

have antibacterial properites

39
Q

The pancreas has a role in digestion but also the post-absorptive use of nutrients. What hormones are released by the pancreas and when?

A

INSULIN and GLUCAGON
- insulin is post absorptive
- glucagon is released during a fasting state when glucose levels are dropping; it acts to release FAs and AAs to maintain glucose profile

40
Q

What is bile produced by and where is it stored?

A

Produced: liver
Stored: gall bladder

41
Q

When is bile released?

A

When chyme enters SI
- gall bladder contracts in response to food ingestion
- emptying peaks ~30 min after a meal

42
Q

What is the fxn of bile?

A

To emulsify dietary fat and activate enzymes to aid in fat digestion

43
Q

How is dietary fat emulsified?

A

Via bile produced by the liver

44
Q

What do the villi of the SI do?

A

increase SA to increase nutrient absorption

45
Q

What is the important about the SI microbiology?

A

Important to prevent colonization of pathogenic microbes

46
Q

When might bacteria in the SI overgrow?

A

With heat-(over)processed diets
- over processed food makes protein difficult to digest. if there is too much undigested protein undesired protein fermentation occurs resulting in diarrhea

47
Q

How is the cat’s SI different from the dog’s?

A

Cat: sugar transport systems NOT adaptive to varying levels of dietary CHOs (true carnivores)
- free sugars and complex CHO are a negligible % of diet
- no energy wasting to change carrier systems
- pancreatic amylase production about 5% of that in dogs
- pancreatic amylase production is relatively non-adaptive in cats = difficult to upregulate glucose levels in SI (which they shouldn’t have to do anyway)
- AA transporters are highly adaptable

Dog as omnivore: sugar transport systems are hgihly adaptive to dietary CHO

48
Q

How does the cat get (blood) glucose?

A

Cat is not eating starch so how is it getting glucose?
GLUCONEOGENESIS!

49
Q

What are the 2 main fxns of the large intestine?

A
  1. absorption of water and electrolytes
  2. fermentation of dietary fiber and undigested nutrients form the SI
50
Q

What are the 3 parts of the LI?

A

Cecum, colon and rectum
- colon is the largest part

51
Q

What is the transit time for dogs and cats in the LI?

A

~12 hrs

52
Q

What are excreted feces made up of?

A
  • undigested food, sloughed cells and other endogenous losses, and bacteria
53
Q

Can the type of diet impact fecal characteristics?

A

YES!
- amount of indigestible matter present is the major factor

54
Q

What does bacterial fermentation in the LI produce?

A
  • SCFA, lactate, CO2, hydrogen gas, and microbial protein
55
Q

What does digesta movement depend on?

A

The diet’s physical and nutritional characteristics

56
Q

How can transit time of digesta be determined?

A

Using indigestible markers
- measure time elapsed from when first fed to first appearance in feces

57
Q

How can you slow down vs speed up digesta flow?

A

Slower = include soluble fiber
Faster = include insoluble fiber (way to reduce constipation)

58
Q

What are incretions?

A

Intestinal Hormones
- related to how digesta flow is controlled

59
Q

What 3 mechanisms are in place to control nutrient flow?

A
  1. incretins (intestinal hormones)
  2. pancreas (pancreatic hormones, enzymes, bicarbonate)
  3. nervous system
60
Q

Incretion 1: Gastrin
(cell type, location of action, primary action, stimulus for secretion)

A

Cell type: Type G

Location: gastric antrum, duodenum

Primary action:
- stimulates: secretion of gastric acid, pepsinogen and glucagon
- inhibits: gastric emptying

Stimulus for secretion:
- peptide and AA’s in stomach
- distension of stomach

61
Q

Incretin 2: CCK
(cell type, location of action, primary action, stimulus for secretion)

A

Cell type: Type I

Location: duodenum, jejunum

Primary action:
- stimulates: pancreatic enzyme secretion and gallbladder contraction
- inhibits: gastric emptying and secretion and relaxes sphincter of Oddi

Stimulus:
- peptides, AA’s and FA’s in duodenum

62
Q

What are the 3 outcomes of control of digested nutrients?

A
  1. nutrient utilization and deposition
  2. satiety
  3. feed intake and feeding behaviour
63
Q

What are 2 additional controls of food intake?

A
  1. taste receptors
  2. nutrient receptors
64
Q

What are the implications of GI tract physiology on ‘regular’ diets for dogs and for cats?

A

Dogs can deal with quantities of starch and fiber (cats cannot)

65
Q
A

ANSC 464 - Companion Animal Nutrition (20 decks)

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