Week 7: Energy Partioning Flashcards
What order does energy partioning go in?
Gross energy - digestible energy - metabolisable energy - net energy
What is gross energy?
energy released as heat when a compound undergoes complete combustion with oxygen in a bomb calorimeter
What does the Gross energy of food depend on?
Degree of oxidation
C + H : O ratio
What is digestible energy?
gross energy of feed minus the gross energy of feces
What is digested and not lost in faeces
What is metabolisable energy?
It is an estimate of the energy available to an animal from digestion of a feed material, expressed in units of megaJoules per kilogram of feed (MJ/kg DM)
Food ingestion results in what?
Heat production
What are some causes of heat incretment?
- Eating (3-6% of ME intake)
- Micrbobial metabolism (7 - 8% ME intake)
- Nutrient metabolism (amount ME varies dpeending on function, protein metabolism accounts for about 10% heat production)
- Subtrate movement against concentration gradient (10% heat incretment ion pumping)
What is Net Engery?
Energy available for useful purposes
What is maintenance net energy used for?
Maintain bodily functions therefore leaves body as heat
What happens to production net energy?
Stored (growth) or leaves body (wool, milk, eggs)
What happens when there is no metabolisable energy intake?
Negative energy retention, so animal uses body reserves
What happens when energy retention is zero?
metabolisable energy is sufficient to meet requirement for body maintaenance
What are k values?
Efficiency values
What is a major energy source for ruminants?
VFA
- used efficiently
- not as eff as glucose
What does efficiency depend on?
WHether fat, protein or carbs are being produced
Can also be altered by the mix of the ration and the balance of the nutrients
