Unit 3 NUTR 3210

what is the purpose of a functional caecum?

- enormous hindgut filled with bacteria

- SCFA provide most of the host energy for fermentation

- site of vitamin production

4 types of digestive systems

- simple (w/o functional caecum)

- simple (w/ functional caecum)

- ruminant

- avian

what is included in the GI tract?

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

3 terms used for CHO digestion

- solubility

- digestibility (host enzymes)

- gut bacteria (their enzymes)

what are the features of a simple system without a functional caecum?

- monogastric

- nutrient dense low fibre diets

- non functioning = don't need to extract more nutrients through caecum

- human, pig, cat, dog

what part of digestion occurs in the mouth?

- food is chewed and mixed with saliva

- enzymes a-amylase and lingual lipase

what step of digestion occurs in the stomach

- low pH

- food becomes chyme

- gastric juices released eg electrolytes, HCl, enzymes

what steps of digestion occur in the small intestine?

- main site of absorption, large surface area

- motility controlled by longitudinal and circular muscles

- pancreatic juice neutralized acidic chyme

- bile acids

what steps of digestion occur in the large intestine?

- fermentation, highest concentration of bacteria

- water absorption

- produces short chain fatty acids

what contributes to small intestine surface area?

- kerckring folds

- villi and crypts

- microvilli

what is the importance of gut bacteria?

used during the fermentation of non digestible CHO

what are the features of a simple system with a functional caecum?

- "pseudo ruminant", hindgut fermenter

- all other regions function like monogastric

- diets with large amounts of fodder and foraging

- horse, rabbit, hamster

what are signs of energy/nutrient deficiency in hindgut fermenters?

- coprophagy (eating feces)

- colonize guts with bacteria

what are the features of the ruminant system?

- 4 regions of stomach

- foregut fermenter

- diet with high quantity of fodder and forage

- other regions function like mono gastric

- cattle, sheep, goat

what are the 4 regions of the ruminant stomach?

1. reticulum

2. rumen

3. omasum

4. abomasum

what are the features of the reticulum?

- honeycomb appearance to capture nutrients and trap foreign materials

- rich in bacteria = fermentation

what are the features of the rumen?

- largest section, rich in bacteria

- papillae increase surface area for absorption

- food mixed, partially broken down, stored temporarily

- 60-80% energy as SCFA

what are the features of the omasum?

- resorption of water and some electrolytes

- filters large particles

what are the features of the abomasum?

- digestive enzymes secreted from gastric glands

- "true stomach"

what are the 2 main characteristics of ruminant digestion?

1. rumination

2. eructation (belching)

what is the purpose of foregut fermentation?

the nutrients produced by bacteria become available for digestion and absorption by the ruminant

what are the advantages of the ruminant system?

- vitamin synthesis

- non protein nitrogen used to make protein

what are the disadvantages of the ruminant system?

- carbs degraded into gases and lost through eructation

- heat production

what are the features of the avian system?

- beak to break up food

- rapid digestion, starve easily

- chicken, turkey, etc

what are the parts of the avian digestive system?

1. crop

2. two chamber stomach

3. small intestine

4. ceca

5. large intestine

6. cloaca

what is the crop?

- enlarged area of esophagus

- temporary food storage

- softens food, regurgitated to feed offspring

what are the two chambers of the avian stomach?

- glandular = proventriculus (gastric enzymes and HCl)

- muscular = gizzard (grind and digest)

what occurs in the ceca?

2 cecum, minor site of bacterial fermentation

what are the features of the avian large intestine?

- short, to connect SI and cloaca

- stores undigested material

- water absorption

what is the cloaca?

where digestive, urinary, and reproductive systems meet

how can we measure digestibility?

calculate the amount of nutrient in the diet to the amount appearing in feces

what is the total collection method?

- allow to adapt to diet over 7-21 days

- isolate for quantitative analyses

- measure intake 3-10 days

- collect and weigh feces

- analyze for nutrient of interest

equation for the total collection method

apparent digestibility coefficient

= (total intake - total feces)/total intake

what are limitations to the total collection method?

- accuracy

- metabolic cages can cause abnormal animal behaviour

- costly equipment, labour intensive

- not feasible for captive wild animals

what is the indicator/marker method?

- use an internal (natural) or external (added) marker

1. adapt to test diet (with marker)

2. collect a feed and fecal sample

3. analyze for marker and nutrient of interest

what are the characteristics of a marker?

- non absorbable

- must not affect/be affected by GI tract

- must mix easily with food

- easily and accurately measured

equation for indicator method

apparent digestibility coefficient

= (A - B)/A

A= ratio nutrient/marker in feed

B= ratio nutrient/marker in feces

what are the disadvantages of apparent digestibility?

- it underestimates true digestibility

- doesn't consider endogenous secretions, gut bacterial growth, digestive enzymes

how do you measure true digestibility?

1. use a test diet

2. switch to zero nutrient diet

3. analyze feces after test diet cleared

4. subtract level of nutrient in feces from zero nutrient diet from test diet

equation for true digestibility

true digestibility coefficient

= [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

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