Nutrition lecture 2 - Digestion and digestibility
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While chemical analysis gives us the molecular composition what does digestibility give us?
the amount or ability the animal has to use the nutrients
Proportion of feed not excreted in the feces which is therefore assumed to be absorbed
Digestibility helps us assess the nutrients?
A high digestibility feed will have what level of feces?
While a lump of coal has extremely high energy how is its digestibility
2 ways to measure digestibility? (very general) and what do they mean?
- In vivo - in the animal
- In vitro - in the lab
2 methods used for measuring digestibility in vivo?
total fecal collection and indiciator method
What are 3 ways to measure digestibility in vitro?
- Artificial rumen
- Gas production
Give a rough breakdown on how to measure digestibility
- Determine how much nutrient is in feed
- measure feed intake
- collect total fecal output
- determine amount of nutrient in feces
- find the difference
- express it as percentage of nutrient intake
Problem with doing digestibility tests on pasture for cows?
Dont know how much they actually ate
Differentiate between apparent and true digestibility
- apparent is what we usually measure with total fecal collection
- true would be our digestibility minus the endogenous components added to feces like sloughed cells mucus etc etc
3 types of endogenous secretions that could make the difference between apparent and true digestibility
- Digestive secretions
- sloughed intestinal cells
2 problems associated with total collection of feces
- Must have accurate estimation of the feed intake of the animal
- must collect all the feces (what about diarhea or huge volume)
Describe how to use an indicator method
- mix in and indigestible indicator at a low and known level
- feed to animal
- Collect sample from feces
- Measure concentration of indicator
- This change in concentration of the indicator should tell you the total digestibility
What are some properties of an ideal marker? (5)
- Cannot be digested
- No metabolic effect
- Uniform excretion
2 internal digestibility markers
2 examples of external digestibility markers
- Chromic oxide
- Titanium oxide
Differentiate between internal and external digestibility markers
internal is part of the feed and external is added to feed for this purpose specifically
What is a huge drawback with in vivo?
Why is it super hard to measure digestibility in wildlife?
Dont know what they are eating
Using the indicator method can you measure both entire dry matter digestibility and that of specific nutrients or only total?
Describe the in vitro in vivo nylon bag cross for measuring digestibility
You have a nylon bag with pore size big enough that digested nutrients and bacteria can get in and undigested particles cannot you can use this to easily measure digestibility
Gas production in vitro methods often involve
The use of a test tube and something to measure gas production
In regards to the nylon bag method for determining digestibility. What does the material found in the nylon bag after the trial represent?
Nylon bag mostly used in?
Describe some of the challanges associated with trying to use nylon bags in pigs nutrition
- Fed to them they chewed it up
- tubed em and they couldnt pass the pyloric sphincter
- Finally put em straight into intestines but this involves missing the stomache so they are now soaked in pepsin and HCL prior
Pig dont have a rumen cannulae they have a?
What would you like to do?
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