Energy systems Flashcards
What do energy systems do? What knowledge is required?
Relates energy intake of animal to its performance to predict:
- performance of animal to energy intake
- energy requirement for performance
Requires knowledge of:
- energy content of feed (most work on ME, not NE)
- energy requirement of animal (most work on NE)
A bit on ruminant energy systems…? Give 2 examples of common ruminant energy systems?
more complex than monogastrics.
early systems had probs.
eg. 1 - UK ARC ME system
- provides estimates on growing, lactating & pregnant sheep & cattle
- food/animal energy expressed as ME/NE
- Uses eq’s. to predict efficiency of ME for maintenance, growth, preg. & lactation
eg. 2 SCA (Aus) energy
- Based on ARC system
- includes modifications for grazing animals
- different kg estimates for forage diets
- includes kwool
- 10% ME added to maintenance when production required (except preg.)
Energy systems are most accurate in which animal? Why?
dairy cow because:
- less variability in diet
- milk fairly consistent
- Aus sys. appears most accurate
Monogastric energy systems…?
tend to be simpler (less variability in food energy, and efficiency of ME)
Pig energy systems…?
system based on NE, ME, DE
NE most accurate if k factors vary with diet
Chook energy systems…?
most based on ME (easy to measure)
Horse energy systems…?
NRC DE system & INRA NE system
Predicting feed ME…?
using animal calorimetry expensive equations developed based on: - fibre, protein, fat content - digestibility - starch
What are the energy requirements…?
Maintenance plus
- growth
- lactation
- pregnancy
- work
Define maintenance & maintenance requirement…?
body composition does not change
produces no product
not in work
maintenance requirement - quantity required for no net gain or loss of nutrient
Define basal metabolism & fasting metabolism…?
PAST EXAM QUESTION
Basal metabolism
- energy expended (heat) for a fasting animal with no activity
- animals offered feed produce extra heat
- fasting metabolism
- influenced by age & sex
Fasting metabolism - Basal metabolism is the energy/heat expended for a fasting animal with no activity. However this is very hard to measure – even confined animals perform some movement. Therefore Fasting metabolism’s definition accepts that there is still some movement. Hence fasting metabolism can be measured whereas basal metabolism is very difficult to measure. more closely related to the surface area of the animal (more area for heat to be lost)
Define maintenance energy…?
amount required for zero energy equilibrium (balance)
calculate from fasting metabolism allowing for exercise & environment
level of feeding will effect
Define ‘energy for growth’?
Requirements vary with age
NE in fat higher than muscle
young animals lay down more muscle than fat (less energy/kg liveweight gain
In horses also depends on whether in training
What are the energy requirements during pregnancy?
higher in last trimester
pattern of foetal growth can be based on expected birth weight
- energy requirement depends on efficiency with which energy is used to deposit conceptus tissue
What are the energy requirements during lactation?
GREATEST energy requirement
May not be able to eat sufficient to meet demands
- fat reserves
- concentrates
After parturition -> milk yield increases while proteins & minerals decrease
Energy requirement calculated days post-partum or based on yield
