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
2
Q
carbs physiological fuel value
A
4 kcal/g
- accounts for 4% energy loss in feces & 0% energy loss in urine
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
4
Q
protein physiological fuel value
A
4 kcal/g
- accounts for 9% energy loss in feces & 20% energy loss in urine
5
Q
to get nutrient calories in food:
A
multiply nutrient content (amount in weight) by physiological fuel value
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
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
8
Q
digestibility coefficient
A
= % digestibility/100
9
Q
glycemic index
A
measure of how quickly a food can make your blood sugar (glucose) rise
10
Q
to calculate TDN, you need:
A
- % nutrient in feed for each nutrient
- digestibility coefficient
- % digestibility (calculated by 1 x 2)
- account for adj energy by multiplying fats x 2.25
- add together values
11
Q
advantages of TDN
A
- established
- familiar
- useful to compare or for classification of feedstuffs
12
Q
disadvantages of TDN
A
- considers only digestive losses but ignores losses in urine, gasses, & heat produced
- not expressed in energy terminology (% or weight, not calories)
- overestimates energy value of forages, esp poor quality ones (significant energy loss during fermentation)
13
Q
main role of animal nutritionists
A
ration formulation
14
Q
info required for ration formulation
A
- 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
- 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.
15
Q
NASEM
A
national academies of science, engineering, & medicine
