Proximate analysis
Determination of crude protein,crude fat,crude fibers,total ash and moisture content in feed sample is called as proximate analysis.
(1)Crude protein
Kjaldhal introduced the method to determine cp in feed sample, having 3 steps:
Digestion
Distillation
Titration
Note:
NPN(non-protein nitrogen) is added in poultry feed but no NPN is actual protein.According to kjaldhal,if we determine Nitrogen content in given sample we can determine CP.
Digestion
Take 1 gram grind sample and add it in kjaldhal Digestion flask(500ml long neck round bottom flask)
Add 20ml conc. Sulphuric acid + 5ml Digestion mixture.
Digestion mixture contain 97% potassium sulfate and 3 parts copper sulfate,it act as catalyst and stops bubbles formation.
Place the solution at low flame for 2 to 2 and half hour, this will simplify the structure.
After heating a light greenish colour solution is obtained about 7-8 ml.
Cool down the solution.
Make volume for distillation process
Distilled water is used to dilute the solution.
If there’s feed sample 100 ml volume is formed and if we have any feed ingredient to determine cp like soyabean meal, canola meal or sunflower meal etc. 200 ml volume is formed because it has more than 25% protein and more acid is used during titration if volume is concentrated.
Distillation
3% boric acid solution w/v , 40% NaOH solution w/v and methyl red indicator are used in distillation process.
Add 500ml distilled water in conical flask and place it on flame to produce steam.
Take 50ml of 3% boric acid solution in separate flask and add 2-3 drops of methyl red indicator.
Add 10ml 40% NaOH solution and 10ml sample solution in long tube of distillation apparatus, heat it indirect by steam produced by water.
After 5 min observe the colour of boric acid solution.
Titration
N normal hydro chloric acid or sulphuric acid is used in titration proces, titrate the boric acid solution until it’s original violet colour is achieved.
Formula for crude protein
% CP= ml of HCl used×0.1×1.4007× dilution factor ×F/ sample weight (g)
Where:
Dilution factor= 10 or 20 _ how much distilled water is added in sample after digestion to form distillation solution.
F is constant= 6.25
(2)Crude Fiber
TÃ ke silver nitrate paper, weight 2 grams sample and add it in beaker.
Add 200ml of 1.25% Hydrochloric acid in beaker ,mix the solution and place it on crude Fiber apparatus for 30-45 min. at medium flame(80 °C), until 150ml solution is remained.
Filter the sample and add it in beaker.
Now, repeat the same step but this time 1.25% NaOH solution is used instead of hydrochloric acid.
Add sample in crucible dish and place it in hot air oven for 2 hours at 130°C.
Take weight W1.
Now place sample in muffle furnace at 800°C for 1.5- 2 hours and take weight W2.
Formula:
% Crude Fiber=(W1-W2)×100/ sample weight
Note:
This test is performed to determine Non- digestable Carbohydrates in feed sample.
Normal value range is 2-6%
(3) Crude Fat
Take filter paper and weight it.
Add 3g of sample and weight the total.W1
Pack the sample and place it in coxhlet apparatus containing 250ml of N-Hexane/Petroleum ether/Di ethyl ether and water circulation system.
Boil sample in coxhlet apparatus for 3 hours.
After this dry it in sunlight and take weight W2.
Formula:
% Crude Fat= (W1-W2)×100/Sample weight
If moisture test is done then use formula
% Crude Fat= resulted CF ×(100- moisture content)/100
Note:
Layer feed has 3-5% CF and broiler feed has 4-4.5%.
(4) Moisture Content in Feed
Grind the sample of feed/feed ingredient.
Take 10g sample, add it in Aluminum petri dish and take weight W1.
Put weight sample in Hot air oven for overnight at 105°C/ 2 hours at 135°C.
Cool down the sample and take weight W2.
Formula:
% moisture=( W1-W2)×100/sample weight
Note:
Normal moisture content range is 8-12%.If more than 12% than fungus(mycotoxin) can grow and if less than 8%indicates that there’s issue of solubility.
(5) Total Ash Test
Take crucible dish and weight it W1
Add 2g of sample.
Burn the sample in dish for 10-15 min at medium flame.
Now place in muffle furnace UpTo 800°C for 1.5 hours.
Take weight W2.
Formula:
% Ash=( W2-W1)×100/sample weight
Note:
Total Ash Test is done to find out Mineral(in-organic) content in feed sample.
Normal value is 9% for Broiler and 13% for Layer.
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