I want to measure the apparent crude protein digestibility in poultry excreta require specific steps to isolate the nitrogen from other sources than the diet (Urine, digestive tract). Are there any methods that doesn't require specific equipment?
you should separate no digested nitrogen and urine nitrogen using Ekman or stotz method or using colostomed birds.
My former collegues Terpstra and de Hart, also developped a method for seperating urinary and feacal nitrogen. See the attached paper for the reference
Article The energy content of full-fat soya beans in meal and pellet...
Thanks, Unfortunately I couldn't find the full papers for the reference.
Terpstra, K. and de Hart, N., 1974. The estimation of urinary nitrogen and faecal nitrogen in poultry excreta. Z. Tierphysiol. Tierernaehr. Futtermittelkd., 32: 306-320.
A originally German journal which probably also has an english title like Animal Physiology and Animal Nutrition
Fecal nitrogen determination:-
The fecal nitrogen was determined following the procedures outlined by Jakobsen et al. (1960).
Principle:
Trichloro-acetic acid will dissolve the non-protein nitrogenous compounds, the protein is then filtered and the residue is subjected to Kjeldahl determination.
Reagents:-
1- sodium borate (dissolve 50 g boric acid + 100 g sodium hydroxide in 385 ml distilled water).
2- Potassium permanganate (dissolve 3.16 g potassium permanganate in 97 ml distilled water).
3- 10% Trichloro-acetic acid.
4- 2% Trichloro-acetic acid.
Apparatus:-
1- Hot air oven. 2- Kjeldahl apparatus.
3- Filtering funnels. 4- Beakers, 300 ml, with glass stirring rods.
5- Ashless filter paper. 6- Water bath.
7- Analytical balance.
Procedure:
1- Add 70 ml distilled water to 2 g of the dried-excreta in 300 ml capacity beaker.
2- Then add 20 ml sodium borate and 6 ml potassium permanganate.
3-The beaker is placed in water bath at a temperature of 50 0C and is stirred for an hour.
4-It's left to settle for one hour at least at room temperature.
5-Add 30 ml 10% trichloro-acetic acid solution and stir with a glass rod.
6-The beaker is left again for one hour at room temperature.
7-Filter through 15 cm ashless filter paper, wash 4 times with 25-30 ml 2% trichloro-acetic acid and for each, in order that the precipitate is free from solution by pressing on it with glass rod covered with plastic.
8-The filter paper containing the sample (on the glass funnel) is dried in an oven at 90 0C.
9-The sample along with the filter paper is digested following the Kjeldahl method for determining the nitrogen.
Apart from elimination of errors in obtaining exact measurements of feed intake and total faeces output in the traditional total collection method, the use of markers to determine nutrient digestibility of feeds in animal species would fit into animal welfare considerations. The external marker chromic oxide has been the prominent marker in the 1960s to evaluate metabolizable energy content of feeds for poultry. A preliminary feeding period of 5 days and collection of a sample representing day and night excreta over a 24 hour period have been suggested as protocol to get reliable results with the use of chromic oxide as marker. However, difficulty in obtaining repeatability between laboratories because of the analytical assay for chromic oxide, variability in results, incomplete and inconsistent recovery in excreta, and hazardous possibilities, resulted in replacement of the chromic oxide marker technique with the method of total excreta collection. Although titanium dioxide, which can be analysed by an accurate and simple colourimetrical assay, has been used in several studies in poultry, only one study has evaluated this marker for recovery (98%) in excreta. The internal marker, acid-insoluble ash, which also could present an external marker when the internal content is aided with the use of siliceous substances, is gaining popularity in recent times, although most studies presented higher digestibility values with this marker in avian species than those derived through the total excreta collection method. Lack of standardisation of analytical assays could partly explain the latter phenomenon. Although crude fibre has presented recovery rates of near 100% in excreta of laying hens and turkeys, fear of possible digestion of this substance by cecal microflora has prevented the further utilisation of this substance as marker. Lignin, determined by digestion in 72% sulphuric acid, presented recovery rates of 99 and 98% in chickens and ostriches, respectively, and similar (P>0.05) results than the total collection method in partridges. The elimination of the use of markers to determine energy metabolizability and nutrient digestibility with avian species have been based on a small number of studies conducted mainly before 1965, and extrapolation of results obtained with other animal species.
We have compared the total collection method towards the chromic oxide indicator to determine the ratio of faecal output to feed intake in the fullfat soybean experiment with both cokcs and broilers (see attachement).
We concluded then, that the chromic oxide method failed to improve precision over the total collection method.
Article The energy content of full-fat soya beans in meal and pellet...
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