Executive summary (maximum 2 sides A4)

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1 MINISTRY OF AGRICULTURE, FISHERIES AND FOOD CSG 15 Research and Development Final Project Report (Not to be used for LINK projects) Two hard copies of this form should be returned to: Research Policy and International Division, Final Reports Unit, Area 6/01 1A Page Street, London SW1P 4PQ An electronic version should be ed to Project sources and incorporation in a Net Energy model Contractor organisation and location Roslin Institute Roslin Midlothian EH25 9PS Total project costs 70,557 Project start date 01/04/00 Project end date 30/09/00 Executive summary (maximum 2 sides A4) This project was relevant to ROAME A LS36 (Improving the sustainability of livestock production through optimal nutrition). It is directed towards: meeting the nutritional requirements of livestock breeds genetically selected for improved performance; identifying alternative sources of nutrients to facilitate production systems that are environmentally and welfare friendly; improving analytical techniques for determining feed composition and nutritive value. It carried forward certain aspects of LS0902, LS0903 and LS0904, which ended on 31 st March The main objective of this project was to compare amino acid digestibilities measured in ileal digesta and in excreta in UK raw materials and to use the information to complete the current stage of development of a computer model to predict the Net Energy value of raw materials and whole diets. This involved measurement of the amino acid digestibilities of a range of ingredients, which will be included in a database used by the computer simulation. Ease of measurement means that excreta (faeces and urine) samples are routinely used used for the measurement of amino acid digestibilities in poultry. A more accurate measure of the availability of the dietary amino acids to the bird is likely to be given by measurement of digestibility at the ileal level. This project was designed to determine whether faecal measurements could replace ileal measurements in growing broiler chickens, largely because faecal collecton is easier and non-terminal. The digestibility values will CSG 15 (Rev. 12/99) 1

2 themselves contribute to current knowledge on the nutritive value of raw materials for poultry. It was found that, in most raw materials and crystalline amino acids, ileal digestibility gave results that fitted better with previous work. Some of the high digestibility values from faecal measurements result from the magnitude of the correction for endogenous losses, which were estimated with fasted birds. On the other hand, ileal digestibilities of crystalline amino acids confirmed that endogenous losses were not a large source of error in ileal measurements. In the case of faecal measurements, it is possible that young broilers give less reliable results than cockerels under such conditions. It may be relevant that a greater proportion of their energy supply under fasting conditions must come from body protein. It is concluded that further development work would have to be done before faecal digestibility measurements can substitute reliably for ileal determinations in broiler chicks given a precise but small amount of food. CSG 15 (1/00) 2

3 Scientific report (maximum 20 sides A4) The objective of this short project (6 months) was to compare amino acid digestibilities measured from ileal and droppings (faeces + excreta) samples in typical poultry feedstuffs of named varieties from the most recent harvest or of recent manufacture (Table 1). The measurements were done with 3-week-old Cobb broiler chickens. Ileal and faecal measurements on each raw material or test substance were near-simultaneous. Faecal digestibilities were measured by total collection. Ileal digestibilities were measured by a marker method. The marker used was 4 g/kg titanium dioxide. Both methods were used on all test materials shown in Table 1. A subset of the test substances were assayed in each of four time-blocks. The combination diet was used in all blocks as an internal standard to check for variation with time between batches of birds or with time. Three-week-old Cobb broiler males were placed in individual metabolism cages and fasted for 24 h to void the gut of any food residues. For the faecal collections for TME and faecal amino acid digestibility, 5 replicate birds were given each material by tubefeeding. 5 g of each foodstuff to be assayed were fed at 08.00h and 12.00h. Trays were placed under each cage for the quantitative collection of droppings. At approximately the same time 5 similar birds were each given 5 g of glucose; from these 5 birds an estimate is derived of endogenous excretion. This allows calculation of true amino acid digestibilities. Water was freely available at all times. The droppings produced by the birds during the precise 48 h subsequent to feeding were quantitatively collected (in 2 collections, 24 h and 48 h), frozen and freezedried.the dried samples were allowed to equilibrate to atmospheric moisture for 24 h, weighed and homogenised by grinding. For the ileal collections for amino acid digestibility, 10 birds were each fed by tube as before. However, these birds were fed at regular intervals throughout the day (08.00h, 12.00h and 16.00h) ensuring a full crop each time. Water was freely available at all times. The contents of the ileum were removed after humanely killing the birds by lethal injection. Ileal samples were bulked (2 birds per replicate) to allow enough sample to be collected for analysis. The measurement obtained is apparent ileal amino acid digestibility as there is insufficient material to measure amino acid lodsses from fasted birds. As before the samples were freeze-dried and homogenised by grinding. Amino acids were analysed by ion exchange chromatography, following acid hydrolysis or performic acid oxidation (the latter for methionine and cystine). Ileal digestibility was much less variable between time blocks than the faecal measurements (Table 4). Many faecal measurements gave an unfeasibly high result (>100%). In most raw materials and crystalline amino acids, ileal CSG 15 (1/00) 3

4 digestibility gave results that fitted better with previous work (Tables 5,6,7,8). Example comparisons are shown graphically in Figures 1, 2 and 3. In the case of wheat, there was a very poor correlation between faecal and ileal measurements (R 2 = 0.04). With field beans, the correlation was good (R 2 = 0.82). With soya beans, the correlation was good over most of the range but was distorted by a single outlier (cystine). Some of the high digestibility values from faecal measurements result from the magnitude of the correction for endogenous losses, which were estimated with fasted birds. On the other hand, ileal digestibilities of crystalline amino acids (Table 8) were usually greater than 90%, confirming that endogenous losses were not a large source of error in ileal measurements. In the case of faecal measurements, it is possible that young broilers give less reliable results than cockerels under such conditions. It may be relevant that a greater proportion of their energy supply under fasting conditions must come from body protein. Any such effect would be exacerbated because even the fed birds are given a relatively small amount of food. It is concluded that further development work would have to be done before faecal digestibility measurements can substitute reliably for ileal determinations in broiler chicks given a precise but rather small amount of food. Test Materials Wheat (Riband) Barley (Delibes) Oats (Valiant) Peas (Elan) Rapeseed meal [double 0] (solvent extracted) Soya bean meal Fish meal Lupins (Arthur) Field beans (Maris Bede) Linseed meal (solvent extracted) Maize gluten meal Table 1. Test raw materials and mixtures Complete diet based on selection of above raw materials (Table 2) Amino acid mixture; with carrier, starch + cellulose (Table 3) 4

5 Table 2. Combination diet. This was made up to function as an internal control between time blocks RAW MATERIAL INCLUSION (g/kg) Wheat 200 Barley 200 Oats 200 Peas 100 rapeseed meal 100 soya meal 100 fish meal 100 Table 3. Crystalline amino acids diet. This was made up with representative crystalline amino acids with starch and cellulose as energy supply and carrier RAW MATERIAL INCLUSION (g/kg) L-lysine HCl 13 DL-methionine 10 L-threonine 10 L-arginine 10 glutamic acid 10 Starch 470 Cellulose 467 Table 4. Ileal and faecal amino acid digestibilities from a mixed diet (Table 2) in successive time blocks Amino Acid Ileal digestibility(%) Faecal digestibility(%) Alanine * Arginine * Aspartic acid Cystine * Glutamic acid Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tyrosine Valine Table 5. Ileal and faecal amino acid digestibilities from cereals 5

6 Wheat Barley Oats Amino Acid Ileal Faecal Ileal Faecal Ileal Faecal Alanine Arginine Aspartic acid Cystine Glutamic acid Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tyrosine Valine Table 6. Ileal and faecal amino acid digestibilities from legumes Peas Beans Lupin Soya bean meal Amino Acid Ileal Faecal Ileal Faecal Ileal Faecal Ileal Faecal Alanine * * * * Arginine Aspartic acid Cystine Glutamic acid Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline * * Serine Threonine Tyrosine Valine

7 Table 7. Ileal and faecal amino acid digestibilities from other plants (rapeseed and linseed) Rapeseed Linseed Amino Acid Ileal Faecal Ileal Faecal Alanine * * * * Arginine Aspartic acid Cystine Glutamic acid Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tyrosine Valine Table 8. Ileal and faecal amino acid digestibilities from animal material, plant byproduct and crystalline amino acids Fish meal Maize gluten meal Amino acid mix Amino Acid Ileal Faecal Ileal Faecal Ileal Faecal Alanine * * * * - - Arginine * * * Aspartic acid Cystine Glutamic acid Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Proline Serine Threonine Tyrosine Valine

8 Wheat Faecal digestibility y = x R 2 = Ileal digestibility Figure 1. The relationship between faecal and ileal measurements of amino acid digestibility in wheat. Each point represents the mean of 5 replicate measurements for an amino acid. 8

9 Beans Faecal digestibility y = x R 2 = Ileal digestibility Figure 2. The relationship between faecal and ileal measurements of amino acid digestibility in field beans. Each point represents the mean of 5 replicate measurements for an amino acid. 9

10 Soya bean Faecal digestibility Ileal digestibility Figure 3. The relationship between faecal and ileal measurements of amino acid digestibility in soya beans. Each point represents the mean of 5 replicate measurements for an amino acid. Please press enter 10