lecture quiz 15: physoilogical fuel values, TDN, & ration formulation Flashcards

1
Q

physiological fuel values

A
  • = calories listen on human label
  • equivalent of ME
  • calculated by subtracting energy lost in excreta (feces & urine) from GE
  • vit C & A no longer required
  • vit D, Ca, Fe, & K still nutrients of concern expressed in quantity & daily value (% out of 2000 Cal diet)
  • human digestibility is high ∴ low energy loss in feces
  • based on nutrient composition
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2
Q

carbs physiological fuel value

A

4 kcal/g

  • accounts for 4% energy loss in feces & 0% energy loss in urine
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3
Q

fats physiological fuel values

A

9 kcal/g

  • accounts for 4% energy loss in feces & 0% energy loss in urine
  • fats have 2.25x more energy than carbs & proteins
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4
Q

protein physiological fuel value

A

4 kcal/g

  • accounts for 9% energy loss in feces & 20% energy loss in urine
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5
Q

to get nutrient calories in food:

A

multiply nutrient content (amount in weight) by physiological fuel value

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6
Q

evaluating calories

A
  • calories are not all the same → foods w/ a low glycemic index are better
    • glycemic index = spike of insulin & BG → measure of how long glucose stays in system
    • high glycemic index = large spike of insulin & BG then fast drop
  • 300 cal from apple is much better than 300 cal from chocolate cake
    • chocolate cake: insulin spikes & BG rises quickly, but void of any nutritional value so hungry again in an hour ∴ leads to overeating
    • apple: steady insulin response & BG increase, full of nutrients body can use ∴ full for at least 2-4h keeping calories under control
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7
Q

total digestible nutrients (TDN)

A
  • old energy system for estimating energy content of diet (energy index)
  • not expressed in calories
  • directly related to energy density of diet
  • digestibility of components must be known, so run digestibility trial & conduct proximal analysis on feed & feces to determine digestibility of CP, CF, EE, & NFE
  • %TDN = % digestibility CP + % digestibility CF + % digestibility NFE + (% digestibility EE x 2.25)
  • digestible EE is multiplied by 2.25 to account for higher energy value (~2.25x more energy than digestible carbs & proteins)
  • does not consider water or ash (no energy)
  • digestibility coefficient = % digestibility/100
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8
Q

digestibility coefficient

A

= % digestibility/100

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9
Q

glycemic index

A

measure of how quickly a food can make your blood sugar (glucose) rise

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10
Q

to calculate TDN, you need:

A
  1. % nutrient in feed for each nutrient
  2. digestibility coefficient
  3. % digestibility (calculated by 1 x 2)
  4. account for adj energy by multiplying fats x 2.25
  5. add together values
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11
Q

advantages of TDN

A
  1. established
  2. familiar
  3. useful to compare or for classification of feedstuffs
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12
Q

disadvantages of TDN

A
  1. considers only digestive losses but ignores losses in urine, gasses, & heat produced
  2. not expressed in energy terminology (% or weight, not calories)
  3. overestimates energy value of forages, esp poor quality ones (significant energy loss during fermentation)
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13
Q

main role of animal nutritionists

A

ration formulation

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14
Q

info required for ration formulation

A
  1. nutrient & energy requirements of the animal
    • where will those come from (NRC, university research & extension publications, textbooks, etc.)
    • age (stage of growth)
    • size
    • activity/work
    • level of production (egg, milk, meat, etc.)
    • envir
  2. nutrient composition & energy values of available feedstuffs
    • how will we know what the feeds contain
    • analysis, NRC (now called NASEM), university research & extension publications, online databases, etc.
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15
Q

NASEM

A

national academies of science, engineering, & medicine

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16
Q

NASEM publications

A
  • contain species-specific requirement tables
  • publishes & updates nutrient & energy requirements for each domestic species
  • estimates are determined by researchers who critically evaluate scientific literature
  • often called nutritionists bible