2 – Biological Energetics Flashcards
Does apparent digestible energy overestimate or underestimate the true energy value of a feed?
- UNDERESTIMATE: high fat and high starch ingredients/feeds
- OVERESTIMATE: high in protein and fiber ingredients/feeds
- *different nutrients result in different quantities of heat increment
What is net energy (NE) recognized as?
- Closest estimate of true energy values b/c it takes heat increment from digestive process and metabolism of feeds into account
What is metabolizable energy (ME)?
- Accounts from losses from
o Urinary energy (urea, uric acid)
o Gaseous energy (methane, H, HS, CO)
o Gill energy (ammonia) - *energy supplied by the feed that remains in the animal for metabolism (usable energy for the animal)
What is the equation for ME?
- ME = DE – (urinary E + gaseous E + gill E)
If a high protein diet, what does that mean in terms of urinary energy?
- Takes more energy to ‘digest’ the proteins (increased urinary energy)
In what species is ME used?
- Poultry
- Dog
- Cat
Excretion of nitrogenous wastes by birds
- Excreted as uric acid directly into cloaca where it is mixed with feces
- Cannot separate fecal from urinary energy
- *high energy costs even with a low protein diet
Why is ME used in dog and cat feeds?
- High protein diet results in high energy losses in urine
What is heat increment?
- Heat produced during digestion of feed, metabolism of nutrients and excretion of waste
o Accounts for energy lost as HEAT - *3 components
What are the 3 components of heat increment?
- Work of digestion
- Heat of fermentation (especially ruminants)
- Nutrient metabolism
What is the equation for NE?
- NE = GE – FE – Urinary E – Gaseous E – Heat Increment
- NE = maintenance energy + production energy
What are the 2 ways to measure heat increment?
- Direct calorimetry
- Indirect calorimetry: more commonly done
- *in a chamber for both
Indirect calorimetry for measuring heat increment
- Use gaseous exchange (O2 consumption, CO2 output) to estimate heat loss
- *measuring gases NOT the heat like in the direct
What is the equation for heat increment?
- = Total heat production in fed MINUS total head produced during fasting
o Total heat production fasting=basal metabolism - = ME – NE
What are the advantages of NE?
- Takes into account metabolic cost of nutrient metabolism
- Allows better prediction of animal performance based on diet formulation
What are the disadvantages of NE?
- Expensive and time consuming to measure NE
What are the two components of net energy?
- Maintenance component
- Production component
What does the maintenance component of net energy consists of?
- Basal metabolism
- Thermoregulation
- Voluntary activity associated with maintenance
What does the production component of net energy consist of?
- growth
- fat deposition
- offspring
- milk
- eggs
- etc.
What are the 3 components for measuring the energy of production?
- Growth: increase in energy contained in the animals body
- Energy content of milk
- Energy content of egg
What are the energy systems ‘used’ in pigs?
- DE commonly used
- Urine, gaseous losses LOW
What are the energy systems ‘used’ in aquaculture?
- DE
- Protein metabolism is very efficient
o Not as much energy need to ‘make ammonia’
What are the energy systems ‘used’ in poultry?
- ME commonly used
- Fecal + urine excreted together
What are the energy systems ‘used’ in ruminants?
- NE used
- Gaseous losses, HI large
