Biological Energetics Flashcards
What is the estimation of apparent energy with high fat and high starch?
Usually underestimate the apparent digestible energy
What is the estimation of apparent energy with high protein and fiber?
Tends to overestimate the apparent digestible energy
Net energy
Recognized as the closest estimate of true energy values because it takes the heat increment from digestive process and metabolism of feeds into account
Metabolizable energy
The energy absorbed by the animal from feed that remains in the animal for metabolism
*accounts for the energy that is absorbed and loss
What are the losses that metabolizable energy accounts for?
-urinary energy (urea, uric acid)
-gaseous energy (methane, hydrogen, hydrogen sulfide, carbon monoxide)
-gill energy (ammonia)
Metabolizable energy eqn
ME= DE- (urinary E + Gaseous E + Gil E)
*Remember: DE accounts for fecal energy loss
Which animals is ME widely used for?
-poultry, dog, cats
**important because of the energy intensive process of urea and uric acid
AND the high protein diets of dogs and cats
Excretion of nitrogenous wastes by birds
Nitrogenous waste excreted as uric acid in birds
-excreted directly into the cloaca and mixed with feces therefore cannot be separated
Heat increment
Accounts for the energy lost as heat during digestion and metabolism
-includes 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
What are the two ways that heat increment can be measured?
- direct calorimetry
- indirect calorimetry
Direct calorimetry
Heat production measured directly
-animal in chamber measuring heat
Indirect calorimetry
Use gaseous exchange (O2 consumption, CO2 output) to estimate heat loss
-animal in chamber measuring the gases
How can you take into account what heat is coming from basal metabolism and what is the actual heat increment?
Measure the animals heat in a chamber after fasting (basal metabolism) and after being fed (heat increment) and then calculate the difference
Heat increment eqn
= Total heat production fed- total heat production fasting
HI= ME- NE
Advantages to net energy
-takes account of the metabolic cost of nutrient metabolism
-allows for a better prediction of animal performance based on diet formulation
Disadvantages of net energy
-expensive and time consuming to measure NE
Two components of net energy
- Maintenance component
- Production component
Maintenance component of net energy
-basal metabolism
-thermoregulation
-voluntary activity associated with maintenance
Production component of Net energy
-growth
-fat deposition
-offspring
-milk
-eggs
etc!
How to measure Growth energy?
Measure the increase in the energy contained in the animals body
How to measure the Milk energy?
Measure the energy content of the milk
How to measure Egg energy?
Measure the energy content of the egg
Energy systems used in pigs
-DE commonly used
-urine, gaseous losses are low
Energy system used in aquaculture
-DE
-protein metabolism is very efficient
Energy system used in poultry
-ME commonly used
-fecal and urine are excreted together
Energy system used in ruminants
NE used
-gaseous losses, HI is large