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15N-Leucine: Health benefits, applications and issues related to ileal endogenous amino acid losses in poultry

  • R.N. SOOMRO (a1) (a2), J. YAO (a1), M.E. ABD EL-HACK (a3), I.H.R ABBASI (a1), R. HU (a1), M. SAEED (a1), M.A. ARAIN (a1), S.A. SOOMRO (a4), X. YANG (a1), J. FOWLER (a5) and M. ALAGAWANY (a3)...


Having accurate data for ileal amino acid digestibility of a feed ingredient is one of the ways to enhance protein and nitrogen utilisation, improve poultry feeding efficiency, and mitigate ammonia emission and pollution in the environment. Moreover, the precise estimation of endogenous amino acid losses (EAAL) depends on formulating diets on digestible amino acid (DAA) basis. Numerous methods have been reported to determine the endogenous fractions including the regression method, the protein-free diet, and the total digestible nitrogen diet. The EAAL determined by these techniques can help in calculated corrected values for amino acid digestibility, termed true digestibility. Certain dietary components that can be called ‘specific losses’ could lead to higher losses than the basal calculation would indicate. To determine the basal plus specific losses (total endogenous losses), some researchers suggested the 15N-dilution method, which allows the determination of the actual digestibility. This method needs more studies and evaluations because there are some controversial issues about this methodology, such as the validity of the 15N-dilution technique when applied to any amino acid or to total nitrogen, the reference pool for the estimation of the labelling of endogenous fractions/secretions, anti-nutritional agents, the effect of bird age, mucin, different cereal grains, as well as the marker itself and the proper assessment. This review will be focused on the above issues, finding that the recently reported 15N isotopes single injection method could be an easy, time-saving, consistent, and reliable methodology for EAAL estimation in poultry.


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ADEDOKUN, S.A., ADEOLA, O., PARSONS, C.M., LILBURN, M.S. and APPLEGATE, T.J. (2008) Standardized ileal amino acid digestibility of plant feedstuffs in broiler chickens and turkey poults using a nitrogen-free or casein diet. Poultry Science 87: 2535-2548.
ADEDOKUN, S.A., ADEOLA, O., PARSONS, C.M., LILBURN, M.S. and APPLEGATE, T.J. (2011) Factors affecting endogenous amino acid flow in chickens and the need for consistency in methodology. Poultry Science 90: 1737-1748.
ADEDOKUN, S.A., LILBURN, M.S., PARSONS, C.M., ADEOLA, O. and APPLEGATE, T.J. (2007a) Effect of age and method on ileal endogenous amino acid flow in turkey poults. Poultry Science 86: 1948-1954.
ADEDOKUN, S.A., PARSONS, C.M., LILBURN, M.S., ADEOLA, O. and APPLEGATE, T.J. (2007b) Endogenous amino acid flow in broiler chicks is affected by the age of birds and method of estimation. Poultry Science 86: 2590-2597.
ADEDOKUN, S.A., PARSONS, C.M., LILBURN, M.S., ADEOLA, O. and APPLEGATE, T.J. (2007c) Comparison of ileal endogenous amino acid flows in broiler chicks and turkey poults. Poultry Science 86: 1682-1689.
ADEDOKUN, S.A., UTTERBACK, P., PARSONS, C.M., ADEOLA, O., LILBURN, M.S. and APPLEGATE, T.J. (2009) Comparison of endogenous amino acid flow in broilers, laying hens and caecectomised roosters. British Poultry Science 50: 359-365.
ADEOLA, O., COWIESON, A.J. and AJUWON, K.M. (2016) . Basal endogenous losses of amino acids in protein nutrition research for swine and poultry. Animal Feed Science and Technology:
ALAGAWANY, M., EL-HINDAWY, M.M. and ATTIA, A.I. (2014a) Impact of protein and certain amino acids levels on performance of growing Japanese quails. Universal Journal of Applied Science 2: 105-110.
ALAGAWANY, M. and MAHROSE, KH.M. (2014) Influence of different levels of certain essential amino acids on the performance, egg quality criteria and economics of Lohmann brown laying hens. Asian Journal of Poultry Science 8: 82-96.
ALAGAWANY, M., ABD EL-HACK, M.E., LAUDADIO, V. and TUFARELLI, V. (2014b) Effect of low-protein diets with crystalline amino acid supplementation on egg production, blood parameters and nitrogen balance in laying Japanese quail. Avian Biology Research 7: 235-243.
ALAGAWANY, M., ABD EL-HACK, M.E., ARIF, M. and ASHOUR, E.A. (2016) Individual and combined effects of crude protein, methionine, and probiotic levels on laying hen productive performance and nitrogen pollution in the manure. Environmental Science and Pollution Research: DOI 10.1007/s11356-016-7511-6.
ALAGAWANY, M., EL-HINDAWY, M.M., ALI, A.A. and SOLIMAN, M.M. (2011) Protein and total sulfur amino acids relationship effect on performance and some blood parameters of laying hens. Egyptian Journal of Nutrition and feeds 14: 477-487.
ANGKANAPORN, K., CHOCT, M., BRYDEN, W.L., ANNISON, E.F. and ANNISON, G. (1994) Effects of wheat pentosans on endogenous amino-acid losses in chickens. Journal of the Science of Food and Agriculture 66: 399-404.
APPLEGATE, T.J., ADEDOKUN, S.A., ADEOLA, O., PARSONS, C.M. and LILBURN, M.S. (2008) Amino acid digestibility-methodology and application, in: Multistate Poultry Feeding Conference, Indianapolis, IN.
BLOUET, C., JO, Y.H., LI, X. and SCHWARTZ, G.J. (2009) Mediobasal hypothalamic leucine sensing regulates food intake through activation of a hypothalamusbrainstem circuit. Journal of Neuroscience 29: 8302-8311.
BOISEN, S. and FERNANDEZ, J.A. (1995) Prediction of the apparent Ileal digestibility of protein and amino-acids in feedstuffs and feed mixtures for pigs by in-vitro analyses. Animal Feed Science and Technology 51: 29-43.
CORZO, A., KIDD, M.T., DOZIER, W.A., PHARR, G.T. and KOUTSOS, E.A. (2007) Dietary threonine needs for growth and immunity of broilers raised under different litter conditions. Journal of Applied Poultry Research 16: 574-582.
COTA, D., PROULX, K., SMITH, K.A., KOZMA, S.C., THOMAS, G., WOODS, S.C. and SEELEY, R.J. (2006) Hypothalamic mTOR signaling regulates food intake. Science 312: 927-930.
COTTEN, B., RAGLAND, D., THOMSON, J.E. and ADEOLA, O. (2016) Amino acid digestibility of plant protein feed ingredients for growing pigs. Journal of Animal Science 94: 1073-1082.
COWIESON, A.J., ACAMOVIC, T. AND BEDFORD, M.R. (2004) The effects of phytase and phytic acid on the loss of endogenous amino acids and minerals from broiler chickens. Brititsh Poultly Science 45: 101-108.
COWIESON, A.J. and RAVINDRAN, V. (2007) Effect of phytic acid and microbial phytase on the flow and amino acid composition of endogenous protein at the terminal ileum of growing broiler chickens. British of Journal Nutrition 98: 745-52.
CRUZAT, V.F., KRAUSE, M. and NEWSHOLME, P. (2014) Amino acid supplementation and impact on immune function in the context of exercise. Journal of the International Society of Sports Nutrition 11: 61.
DALE, N. (1996) Variation in feed ingredient quality: Oilseed meals. Animal Feed Science and Technology 59: 129-135.
DE LANGE, C.F., SAUER, W.C., SOUFFRANT, W.B. and LIEN, K.A. (1992) 15N-leucine and 15N-isoleucine isotope dilution techniques versus the 15N-isotope dilution technique for determining the recovery of endogenous protein and amino acids in digesta collected from the distal ileum in pigs. Journal of Animal Science 70: 1848-1856.
DE LANGE, C.F., SOUFFRANT, W.B. and SAUER, W.C. (1990) Real ileal protein and amino acid digestibilities in feedstuffs for growing pigs as determined with the 15N-isotope dilution technique. Journal of Animal Science 68: 409-418.
DENBOW, D.M. (1985) Food intake control in birds. Neuroscience and Biobehavioral Reviews 9: 223-232.
DIERICK, N.A., VERVAEKE, I.J., DECUYPERE, J.A. and HENDERICKX, H.K. (1986) Influence of the gut flora and of some growth-promoting feed additives on nitrogen metabolism in pigs. II. Studies in vivo . Livestock Prodiction Science 14: 177-193.
DONKOH, A., MOUGHAN, P.J. and MOREL, P.C.H. (1995) Comparison of methods to determine the endogenous amino-acid flow at the terminal ileum of the growing rat. Journal of the Science of Food and Agriculture 67: 359-366.
GABERT, V.M., CANIBE, N., JØRGENSEN, H., EGGUM, B.O. and SAUER, W.C. (1997) Use of 15N-amino acid isotope dilution techniques to determine endogenous amino acids in ileal digesta in growing pigs. Acta Agriculturae Scandinavica 47: 168-177.
GLOAGUEN, M., LE FLOC'H, N., CORRENT, E., PRIMOT, Y. and VAN MILGEN, J. (2012) Providing a diet deficient in valine but with excess leucine results in a rapid decrease in feed intake and modifies the postprandial plasma amino acid and alpha-keto acid concentrations in pigs. Journal of Animal Science 90: 3135-3142.
GOLIAN, A., GUENTER, W., HOEHLER, D., JAHANIAN, H. and NYACHOTI, C.M. (2008) Comparison of various methods for endogenous ileal amino acid flow determination in broiler chickens. Poultry Science 87: 706-712.
GURNSEY, M.P., JAMES, K.A. and JOHNS, D.C. (1985) An improved method of ileal cannulation of adult cockerels. Research Veterinary Science 39: 390-391.
HERMANN, G., MØLLER, L.H., GAMMELGAARD, B., HOHLWEG, J., MATTANOVICH, D., HANN, S. and KOELLENSPERGER, G. (2016) . In vivo synthesized 34S enriched amino acid standards for species specific isotope dilution of proteins. Journal of Analytical Atomic Spectrometry: DOI: 10.1039/c6ja00039h.
HESS, V. and SÈVE, B. (1999) Effects of body weight and feed intake level on basal ileal endogenous losses in growing pigs. Journal of Animal Science 77: 3281-3288.
HESS, V., THIBAULT, J.N. and SÈVE, B. (1998) The 15N amino acid dilution method allows the determination of the real digestibility and of the ileal endogenous losses of the respective amino acid in pigs . Journal of Nutrition 128: 1969-1977.
HODGKINSON, S.M., SOUFFRANT, W.B. and MOUGHAN, P.J. (2003) Comparison of the enzyme-hydrolyzed casein, guanidination, and isotope dilution methods for determining ileal endogenous protein flow in the growing rat and pig. Journal of Animal Science 81: 2525-2534.
HUISMAN, J., HEINZ, T., VAN DER POEL, A.F., VAN LEEUWEN, P., SOUFFRANT, W.B. AND VERSTEGEN, M.W. (1992) True protein digestibility and amounts of endogenous protein measured with the 15N-dilution technique in piglets fed on peas (Pisum sativum) and common beans (Phaseolus vulgaris). British Journal of Nutrition 68: 101-110.
IZUMI, T., KAWAMURA, K., UEDA, H. and BUNGO, T. (2004) Central administration of leucine, but not isoleucine and valine, stimulates feeding behavior in neonatal chicks. Neuroscience Letters 354:166-168.
JANSMAN, A.J., VERSTEGEN, M.W., HUISMAN, J. and VAN DEN BERG, J.W. (1995) Effects of hulls of faba beans (Vicia faba L.) with a low or high content of condensed tannins on the apparent ileal and fecal digestibility of nutrients and the excretion of endogenous protein in ileal digesta and feces of pigs Journal of Animal Science 73: 118-127.
JANSMAN, A.J.M. (1993) Tannins in feedstuffs for simple-stomached animals. Nutrition Research Reviews 6: 209-236.
JANSMAN, A.J.M., SMINK, W., VAN LEEUWEN, P. and RADEMACHER, M. (2002) Evaluation through literature data of the amount and amino acid composition of basal endogenous crude protein at the terminal ileum of pigs. Animal Feed Science and Technology 98: 49-60.
KLUTH, H. and RODEHUTSCORD, M. (2009) Effect of inclusion of cellulose in the diet on the inevitable endogenous amino acid losses in the ileum of broiler chicken. Poultry Science 88: 1199-1205.
KONG, C. and ADEOLA, O. (2013) Ileal endogenous amino acid flow response to nitrogen-free diets with differing ratios of corn starch to dextrose in broiler chickens. Poultry Science 92: 1276-1282.
LETERME, P., SEVE, B. and THEWIS, A. (1998) The current 15N-leucine infusion technique is not suitable for quantitative measurements of ileal endogenous amino acid flows in pigs. Journal of Nutrition 128: 1961-1968.
LIEN, K.A., SAUER, W.C. and DUGAN, M.E. (1997a) Evaluation of the 15N-isotope dilution technique for determining the recovery of endogenous protein in ileal digesta of pigs: effect of the pattern of blood sampling, precursor pools, and isotope dilution technique. Journal Animal Science 75: 159-169.
LIEN, K.A., SAUER, W.C. and FENTON, M. (1997b) Mucin output in ileal digesta of pigs fed a protein-free diet. European Journal of Nutrition 36: 182-190.
LIU, L., SHEN, J., ZHAO, C., WANG, X., YAO, J., GONG, Y. and YANG, X. (2015) Dietary Astragalus polysaccharide alleviated immunological stress in broilers exposed to lipopolysaccharide. International Journal of Biological Macromolecules 72: 624-632.
MAKKAR, H.P. (2008) A review of the use of isotopic and nuclear techniques in animal production. Animal Feed Science and Technology 140: 418-443.
MONTAGNE, L., PLUSKE, J.R. and HAMPSON, D.J. (2003) A review of interactions between dietary fibre and the intestinal mucosa, and their consequences on digestive health in young non-ruminant animals. Animal Feed Science and Technology 108: 95-117.
MONTAGNE, L., PIEL, C. and LALLES, J.P. (2004) Effect of diet on mucin kinetics and composition: nutrition and health implications. Nutrition Review 62: 105-114.
MONTAGNE, L., TOULLEC, R., FORMAL, M. and LALLES, J.P. (2000) Influence of dietary protein level and origin on the flow of mucin along the small intestine of the preruminant calf. Journal of Dairy Science 83: 2820-8228.
MOSENTHIN, R., SAUER, W.C., LIEN, K.A. and DE LANGE, C.F.M. (1993) Apparent, true and real ileal protein and amino acid digestibilities in growing pigs fed two varieties of fababeans (Vicia faba L.) different in tannin content. Journal of Animal Physiology and Animal Nutrition 70: 253-265.
MOTER, V. and STEIN, H.H. (2004) Effect of feed intake on endogenous losses and amino acid and energy digestibility by growing pigs. Journal of Animal Science 82: 3518-3525.
MOUGHAN, P.J. and RUTHERFURD, S.M. (1990) Endogenous flow of total lysine and other amino acids at the distal ileurn of the protein-or peptide-fed rat: The chemical labelling of gelatin protein by transformation of lysine to homoarginine. Journal of the Science of Food and Agriculture 52: 179-192.
MOUGHAN, P.J. and RUTHERFURD, S.M. (2012) Gut endogenous protein-implications for ileal amino acid digestibility determination. British Journal of Nutrition 108: S258-263.
MOUGHAN, P.J., BUTTERY, P.J., ESSEX, C.P. and SOAR, J.B. (1992) Evaluation of the Isotope-Dilution Technique for Determining Ileal Endogenous Nitrogen-Excretion in the Rat. Journal of the Science of Food and Agriculture 58: 165-172.
NYACHOTI, C., DE LANGE, C.F.M., LEESON, S. and GABERT, V. (2000) Endogenous gut nitrogen losses in growing pigs are not caused by increased protein synthesis rates in the small intestine. Journal of Nutrition 130: 566-572.
NYACHOTI, C.M., DE LANGE, C.F.M., MCBRIDE, B.W. and SCHULZE, H. (1997) Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: A review. Canadian Journal of Animal Science 77: 149-163.
ONYANGO, E.M., ASEM, E.K. and ADEOLA, O. (2009) Phytic acid increases mucin and endogenous amino acid losses from the gastrointestinal tract of chickens. British Journal of Nutrition 101: 836-842.
PARSONS, C.M., POTTER, L.M., BROWN, R.D., WILKINS, T.D. and BLISS, B.A. (1982) Microbial contribution to dry matter and amino acid content of poultry excreta. Poultry Science 61: 925-932.
PROUD, C.G. (2004) mTOR-mediated regulation of translation factors by amino acids. Biochemical and Biophysical Research Communications 313: 429-436.
RAVINDRAN, V. (2016) Feed-induced specific ileal endogenous amino acid losses: Measurement and significance in the protein nutrition of monogastric animals. Animal Feed Science and Technology:
RAVINDRAN, V. and BRYDEN, W.L. (1999) Amino acid availability in poultry - in vitro and in vivo measurements. Australian Journal of Agricultural Research 50: 889-908.
RAVINDRAN, V. and HENDRIKS, W.H. (2004) Endogenous amino acid flows at the terminal ileum of broilers, layers and adult roosters. Animal Science 79: 265-271.
RAVINDRAN, V., HEW, L.I., RAVINDRAN, G. and BRYDEN, W.L. (2004) Endogenous amino acid flow in the avian ileum: quantification using three techniques. British Journal of Nutrition 92: 217-223.
REDA, F.M., ASHOUR, E.A., ALAGAWANY, M. and ABD EL- HACK, M.E. (2015) Effects of dietary protein, energy and lysine intake on growth performance and carcass characteristics of growing Japanese quails. Asian Journal of Poultry Science 9: 155-164.
RODEHUTSCORD, M., KAPOCIUS, M., TIMMLER, R. and DIECKMANN, A. (2004) Linear regression approach to study amino acid digestibility in broiler chickens. British Poultry Science 45: 85-92.
ROOS, N., PFEUFFER, M. and HAGEMEISTER, H. (1994) Labeling with 15N as compared with homoarginine suggests a lower prececal digestibility of casein in pigs. Journal of Nutrition 124: 2404-2409.
ROSTAGNO, H.S., PUPA, J.M.R. and PACK, M. (1995) Diet formulation for broilers based on total versus digestible amino acids. The Journal of Applied Poultry Reseach 4: 293-299.
RUTHERFURD, S.M., CUI, J., GORONCY, A.K. and MOUGHAN, P.J. (2015) Dietary protein structure affects endogenous ileal amino acids but not true ileal amino acid digestibility in growing male rats. Journal of Nutrition 145: 193-198.
SAKAMOTO, K., HIROSE, H., ONIZUKA, A., HAYASHI, M., FUTAMURA, N., KAWAMURA, Y. and EZAKI, T. (2000) . Quantitative study of changes in intestinal morphology and mucus gel on total parenteral nutrition in rats. Journal of Surgical Research 94: 99-106.
SAUER, W.C. and OZIMEK, L. (1986) Digestibility of amino acids in swine: Results and their practical applications. A review. Livestock Production Science 15: 367-388.
SCHULZE, H., BUTTS, C.A., MOUGHAN, P.J. and VERSTEGEN, M.W.A. (1995) The 15 N-isotope dilution method for determining ileal endogenous nitrogen excretion in the young (10 kg liveweight) pig. Journal of the Science of Food and Agriculture 69: 41-50.
SCHULZE, H., VAN LEEUWEN, P., VERSTEGEN, M.W.A., HUISMAN, J., SOUFFRANT, W.B. and AHRENS, F. (1994) Effect of level of dietary neutral detergent fiber on ileal apparent digestibility and ileal nitrogen losses in pigs. Journal of Animal Science 72: 2362-2368.
SELLE, P.H., RAVINDRAN, V. and BRYDEN, W.L. (2006) Influence of dietary phytate and exogenous phytase on amino acid digestibility in poultry: a review. Journal of Poultry Science 43: 89-103.
SELLE, P.H., RAVINDRAN, V., CALDWELL, R.A. and BRYDEN, W.L. (2000) Phytate and phytase: consequences for protein utilisation. Nutrition Research Reviews 13: 255-278.
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.
SMIRNOV, A., SKLAN, D. AND UNI, Z. (2004) Mucin dynamics in the chick small intestine are altered by starvation. Journal of Nutrition 134: 736-742.
SOLEIMANI, A.F., KASIM, A., ALIMON, A.R., MEIMANDIPOUR, A. and ZULKIFLI, I. (2010) Ileal endogenous amino acid flow of broiler chickens under high ambient temperature. Journal of Animal Physiology and Animal Nutrition 94: 641-647.
SOUFFRANT, W.B., DARCY, , VRILLON, B., CORRING, T., LAPLACE, J.P., KOHLER, R., GEBHARDT, G. and RERAT, A. (1986) Recycling of endogenous nitrogen in the pig (preliminary results of a collaborative study). Archiv für Tierernährung 36: 269-274.
STEIN, H.H., FULLER, M.F., MOUGHAN, P.J., SÈVE, B., MOSENTHIN, R., JANSMAN, A.J.M., FERNÁNDEZ, J.A. and DE LANGE, C.F.M. (2007b) Definition of apparent, true, and standardized ileal digestibility of amino acids in pigs. Livestock Science 109: 282-285.
STEIN, H.H., PEDERSEN, C., WIRT, A.R. and BOHLKE, R.A. (2005) Additivity of values for apparent and standardized ileal digestibility of amino acids in mixed diets fed to growing pigs. Journal of Animal Science 83: 2387-2395.
STEIN, H.H., SEVE, B., FULLER, M.F., MOUGHAN, P.J. and DE LANGE, C.F. (2007a) Invited review: Amino acid bioavailability and digestibility in pig feed ingredients: terminology and application. Journal of Animal Science 85: 172-180.
TAMMINGA, S., SCHULZE, H., VAN BRUCHEM, J. and HUISMAN, J. (1995) The nutritional significance of endogenous N-losses along the gastro-intestinal tract of farm animals. Archiv für Tierernährung 48: 9-22.
ULLAH, Z., AHMED, G., NISA, M.U. and SARWAR, M. (2016) Standardized ileal amino acid digestibility of commonly used feed ingredients in growing broilers. Asian-Australas Journal of Animal Science: doi: 10.5713/ajas.15.0703.
WANG, D., ZENG, Z., PIAO, X., LI, P., XUE, L., ZHANG, Q., HAN, X., ZHANG, H., DONG, B. and KIM, S.W. (2011) Effects of keratinase supplementation of corn-soybean meal based diets on apparent ileal amino acid digestibility in growing pigs and serum amino acids, cytokines, immunoglobulin levels and loin muscle area in nursery pigs. Archives of Animal Nutrition 65: 290-302.
WANG, S., KHONDOWE, P., CHEN, S., YU, J., SHU, G., ZHU, X., WANG, L., GAO, P., XI, Q., ZHANG, Y. and JIANG, Q. (2012) Effects of “Bioactive” amino acids leucine, glutamate, arginine and tryptophan on feed intake and mRNA expression of relative neuropeptides in broiler chicks. Journal of Animal Science and Biotechnology 3: 27.
XU, M., YAO, J.H., WANG, K.N., MENG, DE L., LUO, D.Y., WU, X.B. and YANG, F. (2011) 3H-leucine single injection method for determining endogenous amino acid losses of broilers. Nutrition 27: 829-832.
YUDKOFF, M. (1997) Brain metabolism of branched-chain amino acids. Glia 21: 92-98.
ZELIG, R. and RIGASSIO RADLER, D. (2012) Understanding the properties of common dietary supplements: clinical implications for healthcare practitioners. Nutrition in Clinical Practice 27: 767-776.
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