nutrition Flashcards
Proximate Analyses def and made of
= analytical methods to assess
feedstuffs.
-made of
1 moisture
2 dry matter:
a.) organic matter: protein, fat, carbs, vitamins
b.) inorganic “ash” material:
minerals
proximate analysis steps
1: calculate dry matter DM
2: do ether extraction for either extract to measure fat
2: measure crude protein with kjeldhl procedure to measure nitrogen.
3: boil EE (either extract) in acid, and alkali to find Crude Fiber CF and Ash
4: Burn-> gives you CF & Ash
units of energy
- Kilocalorie = Energy required to raise the temperature of 1 kg of water 1 oC kcal
- The Calorie used in human nutrition is actually a kcal (Note that it
begins with a capital C)
Calorie=kcal for humans - Joule is used in Europe and scientific publications
(1 calorie = 4.18 joules)
1kcal =4.18 kjoules
Energy Partitioning
- How much energy is there in food?
- How much is available to the animal for biological processes?
- How can we measure it?
- We oxidize it (burn) and measure how much heat it gives off.
Bomb Calorimetry
- Measures the gross energy of a feedstuff
- GE is heat released when CHO, lipids and proteins in feedstuff are burned-off
- Feed + O2 = CO2 + H2O + HEAT
-marterial is burt in bomb calorimeter
Gross Energy (GE)
- The amount of heat released when a substance (feed) is
completely oxidized in a bomb calorimeter - GE = Heat of Combustion
ex. carb 4.2, fat 9.3.
-indigestible feedstuffs (ash, mineral, water) will have GE 0
-limitations of GE: doesn’t tell us if animal can digest it and need to account for energy losses.
Fecal Energy (FE)
- Some feed energy is not absorbed and instead is lost in feces
due to incomplete digestion. - FE = energy contained in feces measured using a bomb
calorimeter - Single largest loss of ingested energy
Digestible Energy calc
Digestible E = Gross E – Fecal E
Digestibility = (DE/GE) x 100
ex. FE= 10 kcal, GE = 100kcal
DE= 100-10=90kcal
digestibility= (90/100)x100=90%
Net energy NE
-the closest estimate of true
energy values because it takes the heat increment from
digestive process and metabolism of feeds into account.
Metabolizable energy
- Not all of the energy the animal absorbs stays in the animal
- Accounts for losses from:
- Urinary energy (urea, uric acid)
- Gaseous energy (methane, hydrogen, hydrogen sulfide, carbon
monoxide) - Gill energy (ammonia) fish
- Energy supplied by the feed that remains in the animal
for metabolism - ME = DE – (Urinary E + Gaseous E + Gill E)
-use any that are relevant to animal, could be all three
Excretion of nitrogenous wastes by birds
-why we measure ME in poultry
* Nitrogenous waste is excreted as uric acid in birds
* Excreted directly into the cloaca where it is mixed with feces
* Cannot separate fecal from urinary energy
Heat increment
- Accounts for energy lost as heat during digestion and
metabolism - Heat increment is the heat produced (energy used)
during digestion of feed, metabolism of nutrients and
excretion of waste. - Components of heat increment:
- Work of digestion
- Heat of fermentation
- Nutrient metabolism
-Heat increment = Total heat production fed – Total heat production fasting or this equation->
-HI = ME - NE
Net energy: calc, advantages, disad.
-accounts for heat increment lost during metabolism
NE = GE - FE – UrinaryE- GaseousE – Heat Increment
- Advantages:
- Takes account of the metabolic cost of nutrient metabolism
- Allows a better prediction of animal performance based on
diet formulation - Disadvantages:
- Expensive and time consuming to measure NE
Measurement of Heat Increment 2 ways
Direct Calorimetry:
* Heat production measured directly: animal in chamber
- Indirect Calorimetry:
- Use gaseous exchange (O2 consumption, CO2 output) to
estimate heat loss
-fuel + O2 –> CO2 + H2O+ HEAT
-if we account for how much CO2 produced we know how much heat produced per molecule of CO2
2 Components of Net Energy
NE= maintenance E + PE
Maintenance Component:
* Basal metabolism
* Thermoregulation
* Voluntary activity associated with
maintenance
Production Component:
* Growth
* Fat deposition
* Offspring
* Milk
* Eggs etc.
