Flashcards in Feed analyses 1 Deck (19):
Dry matter properties...?
Main feed parameter
Proportions vary (20% silages, 90% grains)
Determined by drying a known amount for 16 hours, then reweighing
Organic matter properties...?
Determines ash/mineral content of feed
High values may indicate contamination
Determined by burning combustible material
Describe proximate (Weende) analysis
Combo of analytical procedures from Germany
Still widely used
Many faults - crude fibre
Attempts to isolate water, ash, crude protein/fibre, ether extract...
Crude protein properties...?
Nitrogen x 6.25 = CP value
NaOH added once cool
Contains: true protein AAs, & non-protein nitrogen (urea)
Ether extract (fat extract) properties...?
Fat content of feed
Components extracted: true fats, waxes, alcohols...
Proportion of feed with high energy values
T or F - If ether extract contains a high proportion of fats, method is not valid for estimating energy content
Crude fibre properties...?
mainly structural carbs
Attempts to simulate stomach digestion SI
How is crude fibre determined?
Boil ether extract in acid & base -> filter residue off -> dried & weighed -> difference between dried & ashed = CF
Nitrogen-free extracted properties...?
Useful for est. soluble carb fraction of grains
Measures difference original sample weight & (sum of water, ash ether, crude fibre & protein)
Primarily soluble carbs (sugars & starch)
What is nitrogen-free extract useful for?
Estimating soluble carb fraction of grain (variable for roughages)
Neutral detergent fibre (NDF) process...
Most common measure of fibre
Measures structural components (cellulose, hemicellulose, lignin) by boiling sample in ND solution (remove cell wall contents) -> residue
Acid detergent fibre properties...?
Removes/isolates hemicellulose & cell wall contents
Residue contains cellulose & lignin
NDF - ADF = ?
Describe in vivo digestibility
Difference between dry feed offered & faeces excreted as %
Animals confined or fitted with faecal collection bags
Feed in & poo out recorded over several days
Time consuming & expensive
Indigestible marker (lignin/waxes)
In vitro digestibility
More feasible & time-efficient
Ruminants - Incubate sample in rumen for 2 days -> pepsin 2 days - residue left = indigestible
Horses - strained faecal fluid
In Sacco digestibility?
'Nylon bag' technique -> contains feed incubated in rumen of fistulated animals - good for time studies
Factors affecting digestibility (feed factors)?
Food composition (fibre)
prep - chaffing, crushing, grinding; cooking...