Nutrition lecture 2 - Digestion and digestibility

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  1. While chemical analysis gives us the molecular composition what does digestibility give us?
    the amount or ability the animal has to use the nutrients
  2. Define digestibility
    Proportion of feed not excreted in the feces which is therefore assumed to  be absorbed
  3. Digestibility helps us assess the nutrients?
  4. A high digestibility feed will have what level of feces?
  5. While a lump of coal has extremely high energy how is its digestibility
  6. 2 ways to measure digestibility? (very general) and what do they mean?
    • In vivo - in the animal
    • In vitro - in the lab
  7. 2 methods used for measuring digestibility in vivo?
    total fecal collection and indiciator method
  8. What are 3 ways to measure digestibility in vitro?
    • Artificial rumen
    • Gas production
    • Enzymes
  9. 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
  10. Problem with doing digestibility tests on pasture for cows?
    Dont know how much they actually ate
  11. 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
  12. 3 types of endogenous secretions that could make the difference between apparent and true digestibility
    • Digestive secretions
    • bacteria
    • sloughed intestinal cells
  13. 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)
  14. 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
  15. What are some properties of an ideal marker? (5)
    • Cannot be digested
    • No metabolic effect
    • Uniform excretion
    • Stable
    • inexpensive
  16. 2 internal digestibility markers
    • Lignin
    • Acid insoluble ash
  17. 2 examples of external digestibility markers
    • Chromic oxide
    • Titanium oxide
  18. Differentiate between internal and external digestibility markers
    internal is part of the feed and external is added to feed for this purpose specifically
  19. What is a huge drawback with in vivo?
  20. Why is it super hard to measure digestibility in wildlife?
    Dont know what they are eating
  21. Using the indicator method can you measure both entire dry matter digestibility and that of specific nutrients or only total?
  22. 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
  23. Gas production in vitro methods often involve
    The use of a test tube and something to measure gas production
  24. In regards to the nylon bag method for determining digestibility. What does the material found in the nylon bag after the trial represent?
    Indigestible material
  25. Nylon bag mostly used in?
  26. 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
  27. Pig dont have a rumen cannulae they have a?
    Duodenal cannulae
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Nutrition lecture 2 - Digestion and digestibility
2013-11-28 22:06:15
Nutrition lecture Digestion digestibility

Nutrition lecture 2 - Digestion and digestibility
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