Feed
Reasons to conduct feed analysis
diet formulation to provide balanced diets
to provide analysis for use in estimating available nutrients
to provide information to solve a production problem that may be feed related
to place a market value on a feed
to verify a commercial guarantee
Importance of moisture or dm analysis
Feedstuffs are quite variable in moisture content
contributes to H2O req of animal
high moisture content has negative effects
Feed analysis results on DM basis
Ruminants can utilize NPN
urea as non-protein nitrogen contains 45% N, which is equivalent to ~281% CP
urea toxicity limits feeding
Limit to 2% of the diet
Urea unpalatable, so mix with molasses
Feed sampling is important for what?
Representative sampling from several locations
Minimize possibility of alterations in feed composition during storage
Methods of DM analysis
Oven drying
Moisture meter
Freeze drying
Near infrared reflectance spectroscopy
Ether extract or crude fat
Compounds found in ether extract
and problems
Ground sample is extracted with diethyl ether for 4 hour using Soxhlet extractor
ether soluble material = ether extract
compounds = triglycerides, free fatty acids, cholesterol, fat soluble vitamins, resins, waxes
problems = EE fraction assumed to have high E content, can overestimate the E content if EE has high % of waxes
What to do with a collected feed sample?
Grind to allow for thorough mixing of sample
preserve if needed
record sampling details
send at least 2 samples for analysis to take average
Ash determination
Ash content = mineral content
Only total amount of minerals is measured
useful indicator of diet composition
Crude fiber
Issues with it
Feed components of low digestibility - cellulose, hemi cellulose and lignin
Issues = Not a chemically defined fraction, incomplete extraction of cellulose hemicellulose and lignin which then ends up in the nitrogen free extract, not highly repeatable
Proximate analysis
most common chemical analysis of feeds
Series of analytical procedures that partitions the feed into six fractions
alternative methods of ashing
Minerals such as iodine and selenium are volatile at 500-600 degrees Celsius - could understand mineral content
Wet ashing procedure - OM destroyed by boiling in concentrated perchloric acid
Advantages and disadvantages of proximate analysis
A = requires relatively inexpensive equipment, provides a good general evaluation of feedstuffs, TDN energy system is based on proximate analysis, most of the current nutritional data is based on proximate analysis
D =Does not define individual nutrients, some errors is basic assumptions, time-consuming, gives no indication of digestibility, partitions carbs poorly
The proximate fractions - what nutrients get analyzed
Moisture or DM
Ash
Crude protein
Ether extract or crude fat
Crude fiber
Nitrogen free extract
Determination of crude protein?
Limitations of it?
measures total N content of test feed and uses it to estimate the crude protein content
Assumption that all protein contains 16% N
Assumption that all N comes from protein
Alternative to crude fiber analysis
Detergent extraction system developed by van soest at cornell university
used primarily for forages
Partitions the fiber component into soluble and insoluble carbohydrate