Animal Energetics Flashcards
Does apparent digestible energy over- or under-estimate the true energy value of a feed?
- DE (& ME) usually underestimate energy in high fat & high starch ingredients/feeds
- DE tends to be overestimated for ingredients high in protein & fiber
- different nutrients result in different quantities of heat increment
What is NE?
Net Energy
- it is recognized as the closest estimate of true energy values b/c it takes the heat increment from digestive process & metabolism of feeds into account
What is ME?
Metabolizable Energy
- energy supplied by the feed that remains in the animal for metabolism
- ME = DE - (urinary E + Gaseous E + Gill E)
what are urinary energy (UE) losses?
urea, uric acid
what are gaseous energy (Gas E) losses?
methane, hydrogen sulfide, carbon monoxide
What are gill (GillE) energy losses?
ammonia
What is the ME here? What is the metabolizability?
ME = GE - (FE + UE + GE)
= 100 - (10 + 5 + 2)
= 83 kcal
Metabolizability = 83%
What animals is ME used for in nutrition?
poultry, dogs, cats
Why do we use ME for birds?
- nitrogenous wastes are excreted as uric acid which has a particularly high energy cost
- uric acid is excreted directly into the cloaca & mixed w/ feces, so urinary energy cannot be separated from fecal energy
Why do we use ME in dog & cat feeds?
high protein diets result in high energy losses in urine which need to be accounted for (cant just account for feces
What is heat increment?
the heat produced during digestion of feed, metabolism of nutrients, & excretion of waste (energy lost as heat)
What are the components of heat increment?
- work of digestion
- heat of fermentation
- nutrient metabolism
What is NE?
Net Energy
NE = GE - (FE + UE + GE + Heat Increment)
calculate NE here & net percent of GE
NE = GE - (FE + UE + GE + Heat Increment)
= 100 - (10 + 5 + 2 + 3)
= 80 kcal
NE % of GE = (NE/GE) x 100% = 80%
How do we measure heat increment?
- Direct Calorimetry: heat production measured directly
- Indirect Calorimetry: use gaseous exchange (O2 consumption, CO2 output) to estimate heat loss (Fuel + O2 = CO2 + H2O + HEAT)
How do we measure heat increment using calorimetry?
Heat increment = total heat production fed - total heat production fasted
total heat production fasting = basal metabolism
HI = ME - NE
What are the advantages and disadvantages of measuring net energy?
Advantages
- takes account of the metabolic cost of nutrient metabolism
- allows a better prediction of animal performance based on diet formulation
Disadvantages
- expensive & time consuming to measure
What are the components of net energy?
NE = maintenance E + Production energy
What is the maintenance component of net energy?
- basal metabolism
- thermoregulation
- voluntary activity associated w/ maintenance
What is the production component of net energy?
- growth
- fat deposition
- offspring
- milk
- eggs, etc.
How do you measure the energy of production for growth?
measure the increase in the energy contained in the animal’s body
How do you measure the energy of production for milk?
measure the energy content of the milk
How do you measure the energy of production for eggs?
measure energy content of the egg
What is the complete flow of energy partitioning?
