Week 8 Flashcards
(186 cards)
What factors control food intake?
Physical
- Stomach/rumen/ crop size etc
Chemical
- Glucose, CCK (cholecystokinin) in non ruminants
- VFAs In ruminants
Nervous/hormonal:
- Leptin & ghrelin?
Physiological:
- Energy density
Palatability
Deficiencies
Illness
Heat (hot eat less),
Obesity
Availability
Why do we need to predict/estimate food intake
Diet formulation
Feed availability
Feed budgeting
Reducing feed wastage
Determining stocking densities
Conservation management –how many fields can lay up
How can you optimise voluntary food intake
Clean troughs (so they can get to clean feed), enough trough space
Provide food at all times
Adequate clean potable water (inc feed moisture)
Good quality feed
No moulds/spoilage (optimum mins/vits)
Mixed forages – intakes better of mixes than single type
Short chop length – decreased transit time (decreased digestibility)
Increase palatability
What factors affect digestibility
Food composition
Diet/Ration composition
Preparation
- Rolling, crushing, grinding, alkali (NaOH, Urea/ammonia), heating, micronisation
Enzyme supplementation
Animal factors
- Individual variation
- Species variation
* Forages have higher digestibility for Ruminants than non ruminants (due to bacteria)
* Sheep tend to digest grain better than cattle
* Cattle tend to digest low quality forage better than sheep
Level of feeding
- More eaten faster passage time - less time for digestive action of enzymes gives lower apparent digestibility
- Mainly affects slowly digested components eg cell wall - fibre
What affects grass digestibility
Grass digestibility decreases as grass grows due to more structural carbs and less storage carbs
Describe the impact of lignin on digestibility
High in wood, straw and hay
High resistance to chemical degradation
Will reduce digestibility of closely associated structural polysacchrarides e.g., cellulose
Name the fibre fractions of crude fibre
NDF - neutral detergent fibre
ADF - acid detergent fibre
MADF - modified acid detergent fibre
describe the composition of food
Water
Dry matter
- Inorganic (ash)
* Minerals
- Organic
* Carbohydrates
* Lipids
* Proteins
* Nucleic acids
* Organic acids
* Vitamins
What fractions is feedstuffs broken down into in proximate analysis?
Moisture
Ash
Crude protein (CP)
Crude fibre (NDF, ADF, MADF)
Ether extract (EE)
Nitrogen free extractives (NFE)
Define gross energy of feed
Total energy feed contains
What is digestible energy
Energy from food animal can access
remainder is mainly lignin & other indigestible compounds
What is metabolisable energy
energy available for utilisation by the animal
What is net energy
the proportion of metabolisable energy that can be used for maintenance, growth, lactogenesis, production of wool/hair, growth of a foetus
What is K factor & what does it mean
The conversion efficiency of metabolisable energy into net energy
Some energy is lost as heat during digestion and metabolism
k factor = NE/ME
What is heat increment
the difference between metabolisable energy and net energy
What processes lead to the production of heat increment
Chewing, rumination, digestive motor activity
Production and secretion of digestive juices
Hydrolysis and metabolism of nutrients in lumen and wall of GIT and active transport across
Metabolism of absorbed nutrients and synthesis of macromolecules
What is diet quality/metabolisability
the proportion of gross energy that is metabolisable
q = ME/GE
What is animal production level (APL)
how hard the animal is working above maintenance requirements
As production within animal increases why does efficiency factor (k) decrease
More food must be eaten => GIT transit time decreases => less time to extract available nutrients
Label the metabolisable energy system
What is metabolic rate
expenditure of energy per given time
What is basal metabolic rate
energy expenditure for basic life processes at rest
What is fasting metabolic rate
‘animal’ version of BMR
Usually higher than BMR as movement occurs
What is resting metabolic rate
amount of energy a non-production animal requires to live without gaining or losing weight