Hostname: page-component-76fb5796d-vfjqv Total loading time: 0 Render date: 2024-04-25T15:39:11.930Z Has data issue: false hasContentIssue false
  • English
  • Français

The use of markers to determine energy metabolizability and nutrient digestibility in avian species

Published online by Cambridge University Press:  18 September 2007

J. Sales  and
G.P.J. Janssens
J. Sales*
Affiliation:
Laboratory of Animal Nutrition, Department of Animal Nutrition, Genetics, Breeding and Ethology, Faculty of Veterinary Medicine, Ghent University, Heidestraat 19, B-9820, Merelbeke, Belgium
G.P.J. Janssens
Affiliation:
Laboratory of Animal Nutrition, Department of Animal Nutrition, Genetics, Breeding and Ethology, Faculty of Veterinary Medicine, Ghent University, Heidestraat 19, B-9820, Merelbeke, Belgium
*
*Corresponding author: e-mail: james.sales@rug.ac.be
Get access

Abstract

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.

Keywords

markersdigestibilityavian species
Type
Reviews
Information
World's Poultry Science Journal , Volume 59 , Issue 3 , September 2003 , pp. 314 - 327
Copyright
Copyright © Cambridge University Press 2003

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Almquist, H.J. and Halloran, H.R. (1971) Crude fiber as a tracer in poultry nutrition studies. Poultry Science 50: 1233–1235.Google Scholar
Angel, C.R. (1993) Age related changes in digestibility of nutrients in ostriches and nutrient profiles of ostrich and emu eggs as indicators of nutritional status of the hen and chick. Proceedings of the Association of Avian Veterinarians, Nashville, Tennessee, USA, pp. 275–281.Google Scholar
Atteh, J.O. and Leeson, S. (1985) Response of laying hens to dietary saturated and unsaturated fatty acids in the presence of varying calcium levels. Poultry Science 64: 520–528.Google Scholar
Balloun, S.L. and Khajarern, J.K. (1974) The effects of whey and yeast on digestibility of nutrients in feather meal. Poultry Science 53: 1084–1095.CrossRefGoogle Scholar
Batal, A.B. and Parsons, C.M. (2002) Effect of age on nutrient digestibility in chicks fed different diets. Poultry Science 81: 400–407.Google Scholar
Begin, J.J. and Insko, W.M. Jr. (1972) The effects of dietary protein level on the reproductive performance of Coturuix breeder hens. Poultry Science 51: 1662–1669.CrossRefGoogle Scholar
Bradly, G.L. and Savage, T.F. (1995) The effect of autoclaving a yeast culture of Saccharomyces cerevisiae on turkey poult performance and the retention of gross energy, and selected minerals. Animal Feed Science and Technology 55: 1–7.Google Scholar
Brufau, J., Boros, D. and Marquardt, R.R. (1998) Influence of growing season, tannin content and autoclave treatment on the nutritive value of near-isogenic lines of faba beans (Vicia faba L.) when fed to Leghorn chicks. British Poultry Science 39: 97–105.CrossRefGoogle ScholarPubMed
Chawla, J.S., Lodhi, G.N. and Ichhponani, J.S. (1973) Utilization of oils having different degrees of saturation by chicks. Indian Journal of Animal Science 43: 742–746.Google Scholar
Cheng, T.K. and Coon, C.N. (1990) Research note: Calcium digestibility studies utilizing acid-insoluble ash measurements. Poultry Science 69: 2228–2230.CrossRefGoogle Scholar
Coates, B.J., Slinger, S.J., Summers, J.D. and Bayley, H.S. (1977) Metabolizable energy values and chemical and physical characteristics of wheat and barley. Canadian Journal of Animal Science 57: 195–207.Google Scholar
Dansky, L.M. and Hill, F.W. (1952) Application of the chromic oxide indicator method to balance studies with growing chickens. Journal of Nutrition 47: 449–459.CrossRefGoogle ScholarPubMed
Divakaran, S., Obaldo, L.G. and Forster, I.P. (2002) Note on the methods for determination of chromic oxide in shrimp feeds. Journal of Agricultural and Food Chemistry 50: 464–467.CrossRefGoogle ScholarPubMed
Dove, H. and Mayes, R.W. (1991) The use of plant wax alkanes as marker substances in studies of the nutrition of herbivores: a review. Australian Journal of Agricultural Research 42: 913–952.Google Scholar
Duke, G.E., Petrides, G.A. and Ringer, R.K. (1968) Chromium-51 in food metabolizability and passage rate studies with the ring-neck pheasant. Poultry Science 47: 1356–1364.Google Scholar
Elwell, D. and Soares, J.H. Jr. (1975) Amino acid bioavailability: a comparative evaluation of several assay techniques. Poultry Science 54: 78–85.Google Scholar
Erbersdobler, H. and Riedel, G. (1972) Estimation of amino acid digestibility in germfree and conventionally housed chickens. 1. Archit. fü Geflügelkunde 36: 218–222 (German with English abstract).Google Scholar
Fancher, B.I., Jensen, L.S. and Smith, R.L. (1987) Metabolizable energy content of pearl millet [Pennisetum americanum (L.) Leeke]. Poultry Science 66: 1693–1696.Google Scholar
Farrell, D.J. and Martin, E.A. (1998) Strategies to improve the nutritive value of rice bran in poultry diets. III. The addition of inorganic phosphorus and a phytase to duck diets. British Poultry Science 39: 601–611.CrossRefGoogle Scholar
Farrell, D.J., Sales, J., Perez-Maldonado, R., Kent, P., Shermer, M. and Mannion, P.F. (2000) The apparent metabolisable energy of diets with different sources of fibre when fed to emus, ostriches and cockerels. In: Chwalibog, A., Jakobsen, K. (Eds.), Proceedings of the 15th Symposium on Energy Metabolism in Animals, Copenhagen, Denmark, 11–16 September 2000. EAAP Publication No. 103, Wageningen Press, Wageningen. 2001, pp. 141–143.Google Scholar
Fernandez, E., Tortuero, F. and Martin, L. (1993) The effects of different levels of dietary sepiolite on tibial dyschondroplasia in chickens. Archiv für Geflügelkunde 58: 171–175.Google Scholar
Gongnet, G.P., Niess, E., Rodehutschord, M. and Pfeffer, E. (2001) Algae-meal (Spirulina platensis) from lake Chad replacing soybean-meal in broiler diets. Archiv für Geflügelkunde 65: 265–268.Google Scholar
Halloran, H.R. (1972) A major problem in metabolizable energy determinations of feedstuffs for poultry. Feedstufs 44 (7): 38–39.Google Scholar
Halloran, H.R. and Almquist, H.J. (1973) Metabolizable energy determinations of safflower meals for turkeys. Poultry Science 52: 1674–1676.Google Scholar
Halloran, H.R. and Sibbald, I.R. (1979) Metabolizable energy values of fats measured by several procedures. Poultry Science 58: 1299–1307.Google Scholar
Han, I.K., Hochstetler, H.W. and Scott, M.I. (1976) Metabolizable energy values of some poultry feeds determined by various methods and their estimation using metabolizability of the dry matter. Poultry Science 55: 1335–1342.Google Scholar
Hatt, J-M., Mayes, R.W., Clauss, M. and Lechner-doll, M. (2001) Use of artificially applied n-alkanes as markers for the estimation of digestibility, food selection and intake in pigeons (Columba livia). Animal Feed Science and Technology 94: 65–76.Google Scholar
Hew, L.I., Ravindran, V., Mollah, Y. and Bryden, W.L. (1998) Influence of exogenous xylanase supplementation on apparent metabolisable energy and amino acid digestibility in wheat for broilers. Animal Feed Science and Technology 75: 83–92.Google Scholar
Hill, F.W. and Anderson, D.L. (1958) Comparison of metabolizable energy and productive energy determinations with growing chickens. Journal of Nutrition 64: 587–603.CrossRefGoogle Scholar
Hill, F.W., Anderson, D.L., Renner, R. and Carew, L.B. Jr. (1960) Studies of the metabolizable energy of grain and grain products for chickens. Poultry Science 39: 573–579.CrossRefGoogle Scholar
Hill, F.W. and Renner, R. (1960) The metabolizable energy of soybean oil meals, soybean millfeeds and soybean hulls for the growing chick. Poultry Science 39: 579–583.CrossRefGoogle Scholar
Hill, F.W. and Renner, R. (1963) Effects of heat treatment on the metabolizable energy value of soybeans and extracted soybean flakes for the hen. Journal of Nutrition 80: 375–380.Google Scholar
Horani, F. and Daghir, N.J. (1975) Metabolizable energy (M.E.) values of three protein supplements as determined with chicks and laying hens. Poultry Science 54: 1886–1889.Google Scholar
Jamroz, D., Jakobsen, K., Orda, J., Skorupiñska, J. and Wiliczkiewicz, A. (2001) Development of gastrointestinal tract and digestibility of dietary fibre and amino acids in young chickens, ducks and geese fed diets with high amounts of barley. Comparative Biochemistry and Physiology Part A, 130: 643–652.Google Scholar
Jamroz, D., Jakobsen, K., Bach knudsen, K.E., Wiliczkiewicz, A. and Orda, J. (2002a) Digestibility and energy value of non-starch polysaccharides (NSP) in young chickens, ducks and geese, fed diets containing high amounts of barley. Comparative Biochemistry and Physiology Part A 131: 657–668.CrossRefGoogle ScholarPubMed
Jamroz, D., Wiliczkiewicz, A., Orda, J., Wertelecki, T. and Skorupiñska, J. (2002b) Aspects of development of digestive activity of intestine in young chickens, ducks and geese. Journal of Animal Physiology and Animal Nutrition 86: 353–366.Google Scholar
Kadim, I.T., Moughan, P.J. and Ravindran, V. (2002) Ileal amino acid digestibility assay for the growing meat chicken – comparison of ileal and excreta amino acid digestibility in the chicken. British Poultry Science 44: 588–597.Google Scholar
Kotb, A.R. and Luckey, T.D. (1972) Markers in nutrition. Nutrition Abstracts and Reviews 42: 813–845.Google Scholar
Leone, J.L. (1973) Collaborative study of the quantitative determination of titanium dioxide in cheese. Journal of the Association of Official Analytical Chemists 56: 535–537.Google ScholarPubMed
Lodhi, G.N., Malik, N.S. and Ichhponani, J.S. (1974) Metabolizable energy, nitrogen absorbability and feeding value of expeller processed mustard cake for chicks. British Poultry Science 15: 459–465.Google Scholar
Longstaff, M. and Mcnab, J.M. (1991a) The effect of concentration of tannin-rich bean hulls (Vicia faba L.) on activities of lipase (EC 3.1.1.3) and α-amylase (EC 3.2.1.1) in digesta and pancreas and on the digestion of lipid and starch by young chicks. British Journal of Nutrition 66: 139–147.Google Scholar
Longstaff, M. and Mcnab, J.M. (1991b) The inhibitory effects of hull polysaccharides and tannins of field beans (Vicia fabu L.) on the digestion of amino acids, starch and lipid and on digestive enzyme activities in young chicks. British Journul of Nutrition 65: 199–216.CrossRefGoogle Scholar
Malik, N.S., Chopra, A.K., Lodhi, G.N. and Ichhponani, J.S. (1973) Evaluation of commercial chick rations. Indian Journal of Animal Science 43: 874–877.Google Scholar
Marais, J.P. (2000) Use of markers. In: Mello, J.P.F. (Ed.), Farm Animal Metaholism and Nutrition, CABI International, Wallingford, Oxon, UK, pp. 255–277.Google Scholar
Martin, E.A., Nolan, J.V., Nitsan, Z. and Farrell, D.J. (1998) Strategies to improve the nutritive value of rice bran in poultry diets. IV. Effects of addition of fish meal and a microbial phytase to duckling diets on bird performance and amino acid digestibility. British Poultry Science 39: 612–621.CrossRefGoogle Scholar
Mcdonald, P., Edwards, R.A., Greenhalgh, J.F.D. and Morgan, C.A. (2002) Animal Nutrition, Sixth edtition Pearson Education Limited, Essex, UK. 693 pp.Google Scholar
Mcnab, J.M. (2000) Rapid metabolizable energy assays. In: Mello, J.P.F. (Ed), Farm Animal Metabolism and Nutrition, CABI International, Wallingford, Oxon, United Kingdom, pp. 307–315.Google Scholar
Moniello, G., Pinna, W., Nizza, A., Stanco, G. and Solinas, I.L. (2001) Digestion capabilities and estimation of metabolisable energy of diets in relation to their chemical components in Barbary partridge (Alectoris Barhara). Rivista Avicoltura 70: 37–40 (Italian with English abstract).Google Scholar
Mueller, W.J. (1956) Feasibility of the chromic oxide and the lignin indicator methods for metabolism experiments with chickens. Journal of Nutrition 58: 29–36.CrossRefGoogle ScholarPubMed
Newkirk, R.W., Classen, H.L. and Tyler, R.T. (1997) Nutritional evaluation of low glucosinolate mustard meals (Brussica juncea) in broiler diets. Poultry Science 76: 1272–1277.CrossRefGoogle ScholarPubMed
Nizza, A. and Di Meo, C. (2000) Determination of apparent digestibility coefficients in 6-, 12-and 18-week- old ostriches. British Poultry Science 41: 518–520.Google Scholar
Njaa, L.R. (1961) Determination of protein digestibility with titanium dioxide as indicator substance. Acta Agriculturue Scandinavica 11: 227–241.CrossRefGoogle Scholar
Olsson, N. and Kihlen, G. (1948) Edin's indicator method in digestibility experiments on poultry. Eight World's Poultry Congress, Copenhagen 1: 225–232.Google Scholar
Pan, C.F., Igbasan, F.A., Guenter, W. and Marquardt, R.R. (1998) The effects of enzyme and inorganic phosphorus supplements in wheat- and rye-based diets on laying hen performance, energy, and phosphorus availability. Poultry Science 77: 83–89.CrossRefGoogle ScholarPubMed
Payne, W.L., Kifer, R.R., Snyder, D.G. and Combs, G.F. (1971) Studies of protein digestion in the chicken. 1. Investigation of apparent amino acid digestibility of fish meal protein using cecectomized, adult male chickens. Poultry Science 50: 143–150.Google Scholar
Peddie, J., Dewar, W.A., Gilbert, A.B. and Waddington, D. (1982) The use of titanium dioxide for determining apparent digestibility in mature domestic fowls (Gallus domesticus). Journal of Agricultural Science 99: 233–236.CrossRefGoogle Scholar
Pérez,-vendrell, A.M., Angulo, E. and Brufau, J. (2001) Effects of microbial phytase on apparent retention of phosphorus, calcium and zinc in broilers according to type of diet. Cahiers Options Méditerranéennes 54: 191–195.Google Scholar
Perttilä, S., Valaja, J., Partanen, K. and Jalava, T. (2001a) Effect of volume-weight on apparent ileal and excreta amino acid digestibility and feeding value of barley for poultry. Journal of Animal and Feed Sciences 10: 671–685.Google Scholar
Perttilä, S., Valaja, J., Partanen, K., Jalava, T., Kiiskinen, T. and Palander, S. (2001b) Effects of preservation method and β-glucanase supplementation on ileal amino acid digestibility and feeding value of barley for poultry. British Poultry Science 42: 218–229.Google Scholar
Pesti, G.M., Dale, N.M. and Farrell, D.J. (1988) Research note: A comparison of methods to determine the metabolizable energy of feather meal. Poultry Science 68: 443–446.Google Scholar
Potsubay, J. (1974) Reliability of chromic oxide as a marker in studying utilisation and retention of fat and N by poultry. Keszthelyi Mezogazdadagtudomanyi Kar Kozlemenyei 16: 1–25 (Hungarian with English abstract).Google Scholar
Prada, F., Zogno, M.A. and Ghion, E. (1982) Use of chromic oxide for estimating apparent digestibility of dry matter in turkeys (Meleagris gallopavo). 1. Comparison of administration of the indicator in gelatin capsules or mixed with the feed. Revista da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo 19: 183–188 (Portuguese with English abstract).Google Scholar
Prada, F., Ghion, E. and Zogno, M.A. (1983) Use of chromic oxide for estimating apparent digestibility of dry matter in turkeys (Meleagris gallopavo). 2. Excretion and recovery of chromic oxide administrated in gelatin capsules mixed with the feed. Revista da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo 20: 57–61 (Portuguese with English abstract).Google Scholar
Pryor, W.J. and Conner, J.K. (1966) Energy evaluation of poultry feedstuffs. Australian Veterinary Journal 42: 141–145.CrossRefGoogle ScholarPubMed
Ravindran, V., Hew, L.I., Ravindran, G. and Bryden, W.L. (1999) A comparison of ileal digesta and excreta analysis for the determination of amino acid digestibility in food ingredients for poultry. British Poultry Science 40: 266–274.Google Scholar
Reid, B.L., Svacha, A.J., Dorflinger, R.L. and Weber, C.W. (1972) Non-protein nitrogen studies in laying hens. Poultry Science 51: 1234–1243.CrossRefGoogle Scholar
Roudybush, T., Anthony, D.L. and Vohra, P. (1974) The use of polyethylene as an indicator in determination of metabolizable energy of diets for Japanese quail. Poultry Science 53: 1894–1896.Google Scholar
Rymer, C. (2000) The measurement of forage digestibility in vivo. In: Givens, D.I., Owen, E., Axford, R.F.E., Ohmed, H.M. (Eds.), Forage Evaluation in Rurninants, CABI International, Wallingford, Oxon, UK, pp. 113–132.Google Scholar
Schang, M.J., Sibbald, I.R. and Hamilton, R.M.G. (1983) Comparison of two direct bioassays using young chicks and two internal indicators for estimating the metabolizable energy content of feedingstuffs. Poultry Science 62: 117–124.Google Scholar
Scott, T.A. and Boldaji, F. (1997) Comparison of inert markers [chromic oxide or insoluble ash (CeliteTM)] for determining apparent metabolizable energy of wheat-or barley-based broiler diets with or without enzymes. Poultry Science 76: 594–598.Google Scholar
Scott, T.A. and Hall, J.W. (1998) Using acid insoluble ash marker ratios (diet:digesta) to predict digestibility of wheat and barley metabolizable energy and nitrogen retention in broiler chicks. Poultry Science 77: 674–679.CrossRefGoogle ScholarPubMed
Scott, T.A. and Pierce, A.B. (2001) The effect of storage of cereal grain and enzyme supplementation on measurements of AME and broiler chick performance. Canadian Journal of Animal Science 81: 237–243.Google Scholar
Scott, T.A., Silversides, F.G., Classen, H.L., Swift, M.L., Bedford, M.R. and Hall, J.W. (1998a) A broiler chick bioassay for measuring the feeding value of wheat and barley in complete diets. Poultry Science 77: 456–463.Google Scholar
Scott, T.A., Silversides, F.G., Classen, H.L., Swift, M.L. and Bedford, M.R. (1998b) Comparison of sample source (excreta or ileal digesta) and age of broiler chick on measurement of apparent digestible energy of wheat and barley. Poultry Science 77: 449–455.Google Scholar
Short, F.J., Gorton, P., Wiseman, J. and Boorman, K.N. (1996) Determination of titanium dioxide added as an inert marker in chicken digestibility studies. Animal Feed Science and Technology 59: 215–221.Google Scholar
Shrivastava, V.S. and Talapatra, S.K. (1962) Pasture studies in Uttar Pradesh. II. Use of some natural indicators to determine the plane of nutrition of a grazing animal. Indian Journal of Dairy Science 15: 154–160.Google Scholar
Sibbald, I.R. (1978) Scientists study metabolizable energy variations in swine and poultry diets. Feedstuffs 50 (48): 20–22.Google Scholar
Sibbald, I.R. (1982) Measurement of bioavailable energy in poultry feeding stuffs: A review. Canadian Journal of Animal Science 62: 983–1048.CrossRefGoogle Scholar
Sibbald, I.R. (1987) Estimation of bioavailable amino acids in feedingstuffs for poultry and pigs: A review with emphasis on balance experiments. Canadian Journal of Animal Science 67: 221–300.Google Scholar
Sibbald, I.R. and Slinger, S.J. (1961) Measuring available energy in poultry feeds. Feedstuffs 33 (30): 18.Google Scholar
Sibbald, I.R., Summers, J.D. and Slinger, S.J. (1960) Factors affecting the metabolizable energy content of poultry feed. Poultry Science 39: 544–556.CrossRefGoogle Scholar
Smith, A.J. (1972) Some nutritional problems associated with egg production at high environmental temperatures. 2. The effect of environmental temperature and restricted food intake on the metabolizable energy value of diets for laying pullets. Rhodesian Journal of Agricultural Research 10: 23–29.Google Scholar
Thacker, P.A., Campbell, G.L. and XU, Y. (1994) Composition and nutritive value of acidulated fatty acids, degummed canola oils and tallow as energy sources for starting broiler chicks. Animal Feed Science and Technology 46: 251–260.Google Scholar
Tillman, P.B. and Waldroup, P.W. (1988a) Assessment of extruded grain amaranth as a feed ingredient for broilers. 1. Apparent metabolizable energy values. Poultry Science 67: 641–646.Google Scholar
Tillman, P.B. and Waldroup, P.W. (1988b) Assessment of extruded grain amaranth as a feed ingredient for broilers. 1. Apparent amino acid availability values. Poultry Science 67: 647–651.Google Scholar
Van keulen, J. and Young, B.A. (1977) Evaluation of acid-insoluble ash as a natural marker in ruminant digestibility studies. Journal of Animal Science 44: 282–287.CrossRefGoogle Scholar
Ventura, M.R., Castañon, J.I.R. and Mcnab, J.M. (1994) Nutritional value of seaweed (Ulva rigida) for poultry. Animal Feed Science and Technology 49: 87–92.Google Scholar
Vogtmann, H., Pfirter, H.P. and Prabucki, A.L. (1975) A new method of determining metabolizability of energy and digestibility of fatty acids in broiler diets. British Poultry Science 16: 531–534.Google Scholar
Vohra, P. (1966) Energy concepts for poultry nutrition. World's Poultry Science Journal 22: 6–24.Google Scholar
Vohra, P. (1972) Evaluation of metabolizable energy for poultry. World's Poultry Science Journal 28: 204–214.Google Scholar
Vohra, P. and Kratzer, F.H. (1967) Absorption of barium sulfate and chromic oxide from the chicken gastrointestinal tract. Poultry Science 46: 1603–1604.Google Scholar
Warner, A.C.I. (1981) Rate of passage of digesta through the gut of mammals and birds. Nutrition Abstracts and Reviews 51B: 789–820.Google Scholar
Whitson, D., Carrick, C.W., Roberts, R.E. and Hauge, S.M. (1943) Utilization of fat by chickens – a method for determining the absorption of nutrients. Poultry Science 22: 137–141.Google Scholar
Yaghobfar, A., Boldaji, F. and Csapó, J. (2000) Influence of genotype, sex and age of chickens on metabolisable energy of poultry feeds. Acta Agraria Kaposváriensis 4: 37–51.Google Scholar
Yoshida, M. (1973) Improvement of the procedure to determine gross protein value with growing chicks. 1. Standard protein and basal diet. Japanese Poultry Science 10: 76–85.Google Scholar
Yoshida, M. and Morimoto, H. (1957) Reliability of the chromic oxide indicator method for the determination of digestibility with growing chicks. Journal of Nutrition 61: 31–38.Google Scholar
Yuste, P., Longstaff, M. and Mccorquodale, C. (1992) The effect of proanthocyanidin-rich hulls and proanthocyanidin extracts from bean (Vicia faba L.) hulls on nutrient digestibility and digestive enzyme activities in young chicks. British Journal of Nutrition 67: 57–65.Google Scholar
Zelenka, J. (1997) Effect of sex, age and food intake upon metabolisable energy values in broiler chickens. British Poultry Science 38: 281–284.Google Scholar