Lecture 3 Flashcards by Arden Pappot

What are the three types of digestive system?

Simple system (w/o caecum)
Simple system (w/ functional caecum
Multiple system: Ruminant

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What are the 7 parts of the GI tract?

Mouth, esophagus, stomach, small intestine, large intestine, caecum, rectum

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What is solubility?

Is a carbohydrate soluble in the aqueous environment of the digestive tract?
Yes = soluble, No = insoluble

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What is digestibility?

Does the host organism have the enzymes necessary to digest a carbohydrate?
Digestible CHO vs non-digestible CHO (Fibre)

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What is fermentability?

Do gut bacteria have the enzymes necessary to break down a carbohydrate?
Yes = fermentable, No = non-fermentable

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What are the key features of a simple system without a caecum?

Monogastric
Non-functional caecum
Considered a hindgut fermenter - fermentation occurs in the large intestine
Suited for a nutrient dense, low fibre diet

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What are the features of the oral cavity?

Food is chewed, food is mixed with saliva, the two enzymes alpha-amylase and lingual lipase break down carbs and lipids

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What are the features of the stomach?

The stomach empties every 2-6 hours, the pH of the stomach is 2, the food in the stomach becomes ‘chyme’, the gastric glands in the stomach secrete gastric juice, different cells in the stomach differentiate 4 different regions

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What are the four regions of the monogastric stomach?

Cardia, fundus, body, antrum

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What are the features of the small intestine?

Main site for nutrient digestion and absorption - nutrient gateway
Surface area is 30 m^2
Intestinal motility is controlled by longitudinal (push food forward) and circular (mix and break down food) muscles
Chyme acidity is neutralized by pancreatic juice
Food is digested by pancreatic juice/bile

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What are the features of the large intestine/colon?

Site of fermentation
Production of short chain fatty acids/volatile fatty acids
Site for water absorption

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What are the 3 surface areas of the small intestine?

Kerckring folds - cells are absorbing food through the intestine
VIlli/Crypts
Micro villa - brush boarder

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What are some features of gut bacteria?

Unique to every person
Most bacteria are anaerobic
Bacteria increases as we move along digestive system

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Why are gut bacteria very important?

Fermentation of non-digestible CHO - which produces SCFA

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What are the key features of a simple system with a functional caecum?

Pseudo-ruminant
Hindgut fermenter
Functional Caecum
All other regions of the gut function similar to the monogastric system
Suited for a diet with large amounts of fodder and foraging

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What are the signs of an energy or nutrient deficiency?

Eating feces - mostly in young animals, can symbolize nutrient deficiency but also do it to colonize their guts with bacteria

What are the key features of a multiple system: ruminant?

Foregut fermentation
Large stomach divided into 4 regions
Eat a lot of fodder and forage

What are the four stomachs of a ruminant?

Reticulum, Rumen, Omasum, Abomasum

What is the function of the reticulum?

Honeycomb appearance, can capture nutrients and trap foreign materials that are accidentally swallowed, rich in bacteria (fermentation vat)

What is the function of the rumen?

Largest section of the stomach, rich in bacteria (fermentation vat), have rumen papillae which increase the surface area for more absorption, food is mixed and partially broken down, stored temporarily, 60-80% of total energy is produced here

What is the function of the omasum?

Resorption of water and some electrolytes, filters larger particles, book like pages

What is the function of the abomasum?

‘True stomach’, digestive enzymes secreted from gastric glands

What are the two functions of ruminants?

Rumination
Eruption - belching of methane produced by fermentation

What are the advantages and disadvantages of a ruminant system?

Advantages: Vitamin synthesis (B,K), non-protein nitrogen used for making protein
DIsadvantages: Carbohydrates degraded into gases and lost through eructation, heat production

What are the two techniques used to assess digestibility?

1. Total collection method 2. Indicator method: apparent digestibility, true digestibility

What is digestibility?

Measure of the fraction of a specific nutrient that is extracted by the GI tract

Why is digestibility important?

Prevent deficiency and ensure essential nutrients are available to the organism

What is the total collection method process?

1. Allow the animal to adapt to the diet over a 7-21 day period to get used to the food (adaptation period) 2. Isolate animal for quantitative analysis 3. Measure intake over a 3-10 day period 4. Collect and weigh all feces 5. Analyze for nutrient of interest

What is the formula for the total collection method?

Apparent digestibility coefficient = (Total intake - Total feces)/Total intake

What are the limitations of the total collection method?

Accuracy in measuring food intake, labour intensive, animals confined in costly equipment, not feasible for wild animals

What are the steps to the indicator method?

Use a marker into diet to track: either internal or external 1. Adapt animal to test diet (which contains a marker) 2. Collect a feed and fecal sample 3. Analyze each for marker and nutrient of interest relative to your indicator

What is an internal marker vs an external marker?

Internal: a natural component of the feed External: a component added to the feed

What are the four characteristics of a marker?

1. Non-absorbable 2. Must not affect or be affected by the GIT 3. Must mix easily with the food 4. Easily and accurately measured in samples

What is the formula for the apparent digestibility coefficient?

Apparent digestibility coefficient = (A-B)/A, where A=ratio of nutrient/marker in feed and B=ratio of nutrient/marker in feces Apparent digestibility coeff = (total intake-total feces)/total intake

What are the advantages to the indicator method?

less labour intensive, ideal for wild animals

What is the difference between apparent vs true digestibility?

- apparent digestibility underestimates true digestibility not considered when calculating apparent digestibility: - endogenous secretions (epithelial cells - they have nutrients that go into feces, dying cells that output have vitamins, and will show in the data) - bacterial growth in gut (nutrient synthesis) - digestive enzymes (protein secretion)

What are the 4 steps to true digestibility?

1. Perform digestibility study using a test diet 2. Switch to diet containing none of the nutrient of interest (zero nutrient diet) 3. Analyze feces after test diet is cleared 4. subtract level of nutrient in feces of animals fed the zero nutrient diet from the test diet

What is the formula for true digestibility?

True digestibility coeff = [A-(B-C)]/A A = ratio of nutrient/marker in test diet B = ratio of nutrient/marker in feces C = ratio of nutrient/marker in feces after zero nutrient diet