Nutrients and Their Analysis Flashcards
1
Q
what are the reasons for conducting feed analysis
A
- diet formulation to provide balanced diets
- to provide analysis for use in estimating available nutrients, energy (TDN, net energy)
- to provide information to solve a production problem that may be feed related
- to place a market value on a feed
- to verify commercial guarantee
- legal court cases
2
Q
what are the main nutrient components of feed
A
- water or moisture
- dry matter (DM)
- water % + DM% = 100
3
Q
what are the 2 ways nutrient composition of feeds is expressed
A
- as is basis or wet basis = moisture included in calculations of % nutrients
- DM or moisture free basis - moisture is excluded
4
Q
whats important for feed sampling
A
- representative sampling from several locations
- minimize possibility of alterations in feed composition during storage (sealed containers, freeze sample)
- core sampling
5
Q
what should you do for feed sampling
A
- usually collect more material that is needed for analysis
- grind (if possible) to allow thorough mixing of sampling
- preserve if needed (fridge or freezer)
- record sampling details (sample ID/label, date, source, location, condition, operator, take pictures)
- send at least two samples for analysis, take average
6
Q
what is the most commonn analysis of feeds
A
- proximate analysis
- developed >100 years ago at the weende experimental station in germany
- series of analytical procedures that partitions the feed into 6 fractions
7
Q
what is taken in proximate fractions
A
- moisture (water) or DM
- ash (minerals)
- crude protein
- ether extract or crude fat (lipid)
- crude fibre (less digestible carbs)
- nitrogen-free extract ( more digestible carb)
8
Q
why is moisture or DM analysis important
A
- moisture can vary in moisture content (10% cereal grains vs 65% in barely silage)
- contributes to water requirement of animal ( drinking water is a major source)
- high moisture can have negative effects
9
Q
what are some negative effects of high moisture
A
- can reduce feed (DM) intake
- reduces proportion of other nutrients in feed
- reduces storage life of feed
10
Q
steps in dry matter determination
A
- weigh empty container
- place test feed in container, weigh feed + container
- subtract weight of container from total weight for test feed weight before drying
- place in drying oven (either 105-135% for 2 hours or 55% for 48 hours
- weigh, record weight of container + test feed immediately after drying
- subtract weight of container from total weight fo test weight after drying
- divide the weight of the dry test feed by weight of wet feed
- multiply by 100 to get DM %
11
Q
what are the different methods of drying
A
- oven drying = forced air oven, korster tester, microwave (loss of volatile materials )
- moisture meter
- freeze drying
- near - infrared reflectance spectroscopy (NIRS)
12
Q
what is ash determination
A
- ash content = mineral content
- only total amount of minerals is measured = individual mineral content unknown
- useful indicator of diet composition = confirm addition of mineral premix to a mixed diet
- all combustable material (OM) in test feed is burned off in muffle furnace heated to 500-600 leaving inorganic matter (ash) which contians these minerals
13
Q
how do you determine ash
A
- weigh out a small quantity of test feed into an ashing crucible
- ash in a muffle furnace (500-600) for 5 hours
- weigh the residue
14
Q
what are alternate methods of ashing
A
- minerals such as iodine and selenium are volatile at 500-600C (could underestimate mineral content)
- wet-ashing procedure ( OM destroyed by boiling in concentrated perchloric acid (hazardous)
15
Q
how do you measure crude protein
A
- weigh out 0.5-5 g of test feed
- digest by boiling in concentrated sulfuric acid (1 Hr)
- converts all N to ammonium sulphate - cool, dilute with water, add concentrated NaOH (converts ammonia (NH3) )
- distill NH3 into a known quantity of boric acid (traps NH3)
- titrate distillate with HcL drop-wise to determine N content
- calculate the amount of crude protein in test feed by multiplying the amount of total N by 6.25
16
Q
what is the taco-kjeldahl apparatus
A
- digestion + distillation components in one space-saving apparatus ; blower to exhaust fumes
- always contains 16% proteins
17
Q
what are the limitations of kjeldahl CP determination
A
- the assumption that all protein contains 16% N (use 6.25 with mixed feeds (diets))
- use appropriate conversion factor with individual feed ingredients
- assumption that all N comes from protein (non protein N sources, ruminants Vs non-ruminants)
18
Q
what animal can utilize NPN
A
- ruminants
- urea as non-protein nitrogen (NPN) contains 45% N, which is equivalent to 281% CP ( bacteria in rumen can use NPN to build microbial protein - provides amoni acids at S I)
- urea toxicity limits feeding - mortality
- limit to 2% of diet
- urea unpalatable, mix with malasses
19
Q
what is crude fat
A
- either extract
- or either soluable material
20
Q
how do you determine ether extract
A
- weigh out 1-5 g of test feed
- remove water by oven drying
- extract test feed with diethyl ether in a soxhlet extractor for several hours
- evaporate the ether from the extract and weigh the remainder (residue = ether extract/ crude fat)
- %EE = wt of residue/ wt of original sample X 100
21
Q
what are compounds found in ether extracts
A
- tryglycerides (energy = major source)
- free fatty acids ( energy = major source)
- cholesterol (making steroids and building block for vitamin D)
- fat-soluable vitamins
- resins, waxes ( do not contribute anything to the animal, they are not fat)
22
Q
what are problems with either extract
A
- EE fraction assumed to have high E content
- if EE fraction contains a high % of waxes, resins, then the energy in feed can be over estimated
23
Q
what consists in crude fibre
A
- feed components of low digestibility (cellulose, hemicellulose and lignin)
24
Q
how do you determine crude fibre
A
- weigh 1-5g of ether-extracted test feed
- boil in dilute H2SO4 for 30 minutes; filter; then boil in dilute NaOH for 30 minutes; re filter
- dry residue, weigh (whats left = crude fibre)
- % CF = weight of residue/ weight of feed sample X100
25
Q
what are the issues with crude fibre
A
- not a chemically defined fraction
- some cellulose, hemicellulose and lignin extracted which then ends up in the nitrogen free extract (NFE)
- not highly repeatable
- not used anymore
26
Q
what is nitrogen free extract
A
- FE designed to contain the digestible carbohydrate fraction (starch, sugars)
- no chemical analysis for NFE
- all erroros associated with prior analysis; incomplete extraction of crude fibre
- NFE = 100- (%CP + %EE + %CF + %ASH + %H2O)
27
Q
what are some advantages 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
28
Q
what are soe disadvantages of proximate analysis
A
- does not define individual nutrients
- some errors in basic assumption ( assume all nitrogen is 16%)
- time consuming - can be up to two days
- gives no indication of digestibility
- partitions carbs poorly (i e digestibile Vs indigestible )
29
Q
what are alternates of crude fibre
A
- detergent extraction system developed by Van Soest at cronell university
- used primarily for forages
- partitions the fibre component into soluable and insoluable carbs
(neutral detergent NDF and acid detergent (ADF) fibre )
30
Q
what is in NDF
A
- hemicellulose
- cellulose
- lignin
31
Q
what is ADF
A
- lignin
- cellulose
