3. Feed Analysis Flashcards
Animal Feedstuffs
normally described based on the componenets:
moisture
carbohydrates
protein
lipids
ash
vitamins, nucleic acids
The proximate analysis system
moisture
crude protein
crude fibre
ether extract
ash
nitrogen free extractives
legal basis for declared analysis
Moisture or Dry matter
DM determination
different feeds have different percentage moisture
protein contents on label on as fed bases
e.g. can only compare the protein concentration in dry and tinned cat food at a similar DM
dry cat food, 6-10% moisture
tinned cat food, 78% moisture
laboratories dry feed at 105C for 16 hrs, until weight change stops
DM% ; dry sample weight / original sample weight
moisture meter may be used for grains / forages
Crude Protein
most common method for analysis of total protein concentration in farm and companion animal feeds
protein determination based on N concentration
assume all protein contains 16% N
CP=N%x6.25
however, there is N in more than just protein
Kjeldhal method
all feed nitrogen converted to ammonia
CP concentration based on N concentration which is based on ammonia concentration
Feed CP%
Wheat 12.4
Young grass 15.6
Barley straw 3.8
Soyabean meal 50.3
Blood meal 91.9
Whiskas canned kitten 8.0
Ether Extract or Crude Fat %
a crude estimate of the total lipid concentration in feeds
lipids: soluble in organic solvents
feed is rinsed for a pre-determined period with petroleum ether
petroleum ether evaporated off, left with feed less the oil
ether extract also contains:
organic acids, pigments, sterols, vitamins A,D,E,K
contains variable levels of essential fatty acids and fat soluble vitamins, increases feed energy content
Crude Fibre
crude fibre % is an approximation of plant cell wall % in farm and companion animal feedstuffs
determination based on sucessively boiling sample in acid then alkali and weighing the residue
does not contain all of the cell wall (cellulose, hemicellulose and lignin)
good relationship with how much feed is digested
indicates how much indigestible bulk is supplies by the diet
energy digestibility of dry dog food = 94-(4.04 x CF%)
Feed CF%
Wheat straw 41.7
Barley grain 5.3
Sunflower meal (with hulls) 32.3
Meat and bone meal 0
Meat meal 0
Pedigree complete adult (dry) 3%
Ash
an estimate of total inorganic matter or mineral concentration in feeds
essential mineral elements;
major : Ca, P, Mg, S, Na, K, Cl
trace : Cu, Co, I, Zn
non-essential elements : Al, Pb etc.
feed placed in furnace for 4hrs at 550 - 600C
contributes nothing to energy value
organic matter % = 100-ash%
contains material of organic origin
OM determination is important as OM is the energy yielding component of animal feed and is extensively used in farm animal nutrition
Nitrogen-Free Extractives
100-moisture%-ash%-CP%-CF%-EE% = NFE%
carbohydrate component of feed digestible by mammalian enzymes
supposed to measure readily digestible feed carbohydrate
primarily: starches, sugars, pectins, organic acids, pigments
also contains some cellulose, hemicellulose and lignin
NFE: easy way to determine utilisable feed e.g. used to estimate the energy value of horse/companion diets
barely NFE% = 68.5%, poor hay NFE% = 38.3, Fish meal NFE% = 1%
Modern analytical techniques
proximate analysis
used for 100yrs
assigns food to general category
rapid and cheap
legal significance in many countries
starting point of food/ nutrient analysis
CF and NFE inaccurate
very non specific
Fibre analysis
Van Soest detergent system
plant cell walls and plant cell contents
based on the use of detergents and acids
neutral detergent fibre
acid detergent fibre
acid detergent lignin
developed for forage based ruminant diets now used for many feeds and almost all species in feed description
gets rid of cell content, not cell wall
Van Soest Detergent System
structural carbohydrates
-plant cell wall
-digest slowly and not completely
–neutral detergent fibre: cellulose, hemicellulose, lignin
–acid detergent fibre: cellulose, lignin
–acid detergent lignin: lignin
plant cell contents
non structural carbohydrates
digests quickly and completely
-starch
-sugars
-pectin
Neutral detergent fibre
measure of total cell wall carbohydrates
structural carbohydrate or fibre
but contains small concentrations of fibre bound protein: lignified nitrogen: minerals: cutin
feed boiled in sodium lauryl sulphate and EDTA
the residue is NDF
most accurate measure of fibre
indicates digestibility, filling effect, rate of digestion
Van Soest Detergent System
acid detergent fibre ADF
-feed boiled as for NDF but with sulphuric acid
-ADF residue is cellulose and lignin
-less digestible than NDF
-good relationship with digestibility
acid detergent lignin ADL
very strong acid used to leave lignin only as the residue
most indigestible part of cell wall
reduces digestibility of cell wall
amino acids, fatty acids, vitamins
concentrations determined using chromaphotography
gas- liquid chromaphotography: fatty acids e.g. linoleic acid or taurine
high-performance liquid chromaphotography: amino acids, lysine in pig creep
mobile phase gas or liquid passes through column (heated to >350C)
HPLC mobile phase forced through column rapidly
column has resin with adhesive action
separated carbohydrates, fatty acids, amino acids exit column at different times based on physical properties
detection devices generate electrical signal based on number of carbon atoms that exit column at different times
Minerals and Trace Elements
ash little info on mineral types in foods
atomic absorption spectroscopy
acid solution of sample heated in a flame
UV lamp for e.g. Cu emits radiation at specific wavelength
vaporised atoms absorb light
amount of light absorbed proportional to concentration of element
