1. Graham PM, Ott EA, Brendemuhl JH, TenBroeck SH. The effect of supplemental lysine and threonine on growth and development of yearling horses. J Anim Sci 1994; 72:380–6.
https://doi.org/10.2527/1994.722380x
3. Tanner SL, Wagner AL, Digianantonio RN, Harris PA, Sylvester JT, Urschel KL. Dietary crude protein intake influences rates of whole-body protein synthesis in weanling horses. Vet J 2014; 202:236–43.
https://doi.org/10.1016/j.tvjl.2014.06.002
4. Committee on Nutrient Requirements of Horses, National Research Council. Nutrient requirements of Horses. 6th edWashington, DC, USA: National Academy Press; 2007.
5. Committee on Nutrient Requirements of Horses, National Research Council. Nutrient requirements of horses. 5th edWashington, DC, USA: National Academy Press; 1989.
6. Sticker LS, Thompson DL, Bunting LD, Fernandez JM, DePew CL. Dietary protein and(or) energy restriction in mares: plasma glucose, insulin, nonesterified fatty acid, and urea nitrogen responses to feeding, glucose, and epinephrine. J Anim Sci 1995; 73:136–44.
https://doi.org/10.2527/1995.731136x
7. Bryden W. Amino acid requirements of horses estimated from tissue composition. Proceedings of the Nutrition Society of Australia 1991. Danvers, MA, USA: HEC Press; 1991. 16:p. 53
8. Ott EA, Kivipelto J. Growth and development of yearling horses fed either alfalfa or coastal bermudagrass: hay and a concentrate formulated for bermudagrass hay. J Equine Vet Sci 2002; 22:311–9.
https://doi.org/10.1016/S0737-0806(02)70079-8
9. van Niekerk FE, van Niekerk CH. The effect of dietary protein on reproduction in the mare. II. Growth of foals, body mass of mares and serum protein concentration of mares during the anovulatory, transitional and pregnant periods. J S Afr Vet Assoc 1997; 68:81–5.
https://doi.org/10.4102/jsava.v68i3.881
10. van Niekerk FE, van Niekerk CH. The effect of dietary protein on reproduction in the mare. III. Ovarian and uterine changes during the anovulatory, transitional and ovulatory periods in the non-pregnant mare. J S Afr Vet Assoc 1997; 68:86–92.
https://doi.org/10.4102/jsava.v68i3.882
11. Martin RG, McMeniman NP, Dowsett KF. Effects of a protein deficient diet and urea supplementation on lactating mares. J Reprod Fertil Suppl 1991; 44:543–50.
14. Rusoff LL, Lank RB, Spillman TE, Elliot HB. Non-toxicity of urea feeding to horses. Vet Med Small Anim Clin 1965; 60:1123–6.
15. Slade LM, Robinson DW, Casey KE. Nitrogen metabolism in nonruminant herbivores. I. The influence of nonprotein nitrogen and protein quality on the nitrogen retention of adult mares. J Anim Sci 1970; 30:753–60.
https://doi.org/10.2527/jas1970.305753x
17. Hintz HF, Lowe JE, Clifford AJ, Visek WJ. Ammonia intoxication resulting from urea ingestion by ponies. J Am Vet Med Assoc 1970; 157:963–6.
19. Potter GD, Huchton JD. Growth of yearling horses fed different sources of protein with supplemental lysine. In : Proceedings of the 4th Equine Nutrition and Physiology Society Symposium; 1975; p. 19–20.
21. Harper M, Swinker A, Staniar W, Welker A. Ration evaluation of Chesapeake Bay watershed horse farms from a nutrient management perspective. J Equine Vet Sci 2009; 29:401–2.
https://doi.org/10.1016/j.jevs.2009.04.101
23. Committee on Animal Nutrition, National Research Council. Air emissions from animal feeding operations: current knowledge, future needs. Washington, DC, USA: National Academy Press; 2003.
24. Pickrell JA. Hazards in confinement housing: gases and dusts in confined animal houses for swine, poultry, horses and humans. Vet Hum Toxicol 1991; 33:32–9.
26. Leheska JM, Wulf DM, Clapper JA, Thaler RC, Maddock RJ. Effects of high-protein/low-carbohydrate swine diets during the final finishing phase on pork muscle quality. J Anim Sci 2002; 80:137–42.
https://doi.org/10.2527/2002.801137x
27. Connysson M, Muhonen S, Lindberg JE, et al. Effects on exercise response, fluid and acid-base balance of protein intake from forage-only diets in standardbred horses. Equine Vet J Suppl 2006; 38:648–53.
https://doi.org/10.1111/j.2042-3306.2006.tb05620.x
29. McArdle WD, Katch FI, Katch VL. Exercise physiology: nutrition, energy, and human performance. Baltimore, MD, USA: Lippincott Williams & Wilkins; 2010.
30. Kern DL, Slyter LL, Leffel EC, Weaver JM, Oltjen RR. Ponies vs. steers: microbial and chemical characteristics of intestinal ingesta. J Anim Sci 1974; 38:559–64.
https://doi.org/10.2527/jas1974.383559x
31. Gibbs PG, Potter GD, Schelling GT, Kreider JL, Boyd CL. Digestion of hay protein in different segments of the equine digestive tract. J Anim Sci 1988; 66:400–6.
https://doi.org/10.2527/jas1988.662400x
33. Woodward AD, Holcombe SJ, Steibel JP, Staniar WB, Colvin C, Trottier NL. Cationic and neutral amino acid transporter transcript abundances are differentially expressed in the equine intestinal tract. J Anim Sci 2010; 88:1028–33.
https://doi.org/10.2527/jas.2009-2406
35. Ganapathy V, Brandsch M, Leibach FH. Intestinal transport of amino acids and peptides. Johnson LR, editorPhysiology of the gastrointestinal tract. New York, NY, USA: Raven Press; 1994. p. 1773–94.
38. Reitnour CM, Salsbury RL. Effect of oral or caecal administration of protein supplements on equine plasma amino acids. Br Vet J 1975; 131:466–73.
39. Freeman DE, Donawick WJ.
In vitro transport of cycloleucine by equine cecal mucosa. Am J Vet Res 1991; 52:539–42.
40. Freeman DE, Kleinzeller A, Donawick WJ, Topkis VA. I
n vitro transport of L-alanine by equine cecal mucosa. Am J Vet Res 1989; 50:2138–44.
41. Woodward AD, Fan MZ, Geor RJ, McCutcheon LJ, Taylor NP, Trottier NL. Characterization of L-lysine transport across equine and porcine jejunal and colonic brush border membrane. J Anim Sci 2012; 90:853–62.
https://doi.org/10.2527/jas.2011-4210
42. Lewis AJ, Bayley HS. Amino acid bioavailability. Ammerman CB, Baker DH, Lewis AJ, editorsBioavailability of nutrients for animals, amino acids, minerals, and vitamins. New York, NY, USA: Academic Press; 1995. p. 35–65.
43. Stein HH, Seve B, Fuller MF, et al. Invited review: Amino acid bioavailability and digestibility in pig feed ingredients: terminology and application. J Anim Sci 2007; 85:172–80.
https://doi.org/10.2527/jas.2005-742
44. Nyachoti CM, de Lange CFM, McBride BW, Schulze H. Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: a review. Can J Anim Sci 1997; 77:149–63.
https://doi.org/10.4141/A96-044
45. Satchithanandam S, Vargofcak-Apker M, Calvert RJ, Leeds AR, Cassidy MM. Alteration of gastrointestinal mucin by fiber feeding in rats. J Nutr 1990; 120:1179–84.
https://doi.org/10.1093/jn/120.10.1179
46. Myrie SB, Bertolo RF, Sauer WC, Ball RO. Effect of common antinutritive factors and fibrous feedstuffs in pig diets on amino acid digestibilities with special emphasis on threonine. J Anim Sci 2008; 86:609–19.
https://doi.org/10.2527/jas.2006-793
47. Jansman AJM, Smink W, Van Leeuwen P, Rademacher M. Evaluation through literature data of the amount and amino acid composition of basal endogenous crude protein at the terminal ileum of pigs. Anim Feed Sci Techol 2002; 98:49–60.
https://doi.org/10.1016/S0377-8401(02)00015-9
50. Farley EB, Potter GD, Gibbs PG, Schumacher J, Murray-Gerzik M. Digestion of soybean meal proteinin the equine small and large intestine at various levels of intake. J Equine Vet Sci 1995; 15:391–7.
https://doi.org/10.1016/S0737-0806(07)80483-7
51. Hintz HF, Schryver HF, Lowe JE. Comparison of a blend of milk products and linseed meal as protein supplements for young growing horses. J Anim Sci 1971; 33:1274–7.
https://doi.org/10.2527/jas1971.3361274x
52. Latham CM, Wagner AL, Urschel KL. Effects of dietary amino acid supplementation on measures of whole-body and muscle protein metabolism in aged horses. J Anim Physiol Anim Nutr (Berl) 2019; 103:283–94.
https://doi.org/10.1111/jpn.12992
53. Yoshida T, Ohta Y. Estimation of dietary threonine requirement using plasma amino acid concentrations in mature thoroughbreds. Anim Sci J 2018; 89:625–7.
https://doi.org/10.1111/asj.12975
54. Mok CH, Levesque CL, Urschel KL. Using the indicator amino acid oxidation technique to study threonine requirements in horses receiving a predominantly forage diet. J Anim Physiol Anim Nutr (Berl) 2018; 102:1366–81.
https://doi.org/10.1111/jpn.12927
55. Simic P, Willuhn J, Sahm H, Eggeling L. Identification of
glyA (encoding serine hydroxymethyltransferase) and its use together with the exporter ThrE to increase L-threonine accumulation by Corynebacterium glutamicum. Appl Environ Microbiol 2002; 68:3321–7.
http://doi.org/10.1128/AEM.68.7.3321-3327.2002
56. Lodish H, Berk A, Zipursky SL, et al. Section 32, Folding, modification, and degradation of proteins. Freeman WH, editorMolecular cell biology. 4th edNew York, NY, USA: WH Freeman; 2002.
61. Voet D, Voet JG. Biochemistry. 4th EdNewYork, NY, USA: John Wiley& Sons Inc; 2010.
65. Lafitte G. Structure of the gastrointestinal mucus layer and implications for controlled release and delivery of functional food ingredients. Garti N, editorDelivery and controlled release of bioactives in foods and nutraceuticals. New York, NY, USA: CRC Press; 2008. p. 26–52.
66. Almeida FQ, Valdares Filho SC, Donzele JL, et al. Prececal digestibility of amino acids in diets for horses. In : Proceedings of the 16th Equine Nutrition and Physiology Symposium; 1999; p. 274–9.
67. Hendriks WH, Moughan PJ, Tarttelin MF. Gut endogenous nitrogen and amino acid excretions in adult domestic cats fed a protein-free diet or an enzymatically hydrolyzed casein-based diet. J Nutr 1996; 126:955–62.
https://doi.org/10.1093/jn/126.4.955
68. Bertolo RFP, Chen CZL, Law G, Pencharz PB, Ball RO. Threonine requirement of neonatal piglets receiving total parenteral nutrition is considerably lower than that of piglets receiving an identical diet intragastrically. J Nutr 1998; 128:1752–9.
https://doi.org/10.1093/jn/128.10.1752
72. Kim SW, Baker DH, Easter RA. Dynamic ideal protein and limiting amino acids for lactating sows: the impact of amino acid mobilization. J Anim Sci 2001; 79:2356–66.
https://doi.org/10.2527/2001.7992356x
74. Block RJ, Bolling D. Nutritional opportunities with amino acids. J Am Diet Assoc 1944; 20:69–76.
75. Baker DH. Problems and pitfalls in animal experiments designed to establish dietary requirements for essential nutrients. J Nutr 1986; 116:2339–49.
https://doi.org/10.1093/jn/116.12.2339
76. Zello GA, Wykes LJ, Ball RO, Pencharz PB. Recent advances in methods of assessing dietary amino acid requirements for adult humans. J Nutr 1995; 125:2907–15.
https://doi.org/10.1093/jn/125.12.2907
79. Staniar WB, Kronfeld DS, Wilson JA, Lawrence LA, Cooper WL, Harris PA. Growth of thoroughbreds fed a low-protein supplement fortified with lysine and threonine. J Anim Sci 2001; 79:2143–51.
https://doi.org/10.2527/2001.7982143x
81. Rand WM, Young VR, Scrimshaw NS. Change of urinary nitrogen excretion in response to low-protein diets in adults. Am J Clin Nutr 1976; 29:639–44.
https://doi.org/10.1093/ajcn/29.6.639
82. Ellis AD, Hill J. Nutritional physiology of the horse. Nottingham, UK: Nottingham University Press; 2005.
83. Antilley TJ, Potter GD, Gibbs PG, Scott BD, Claborn LD. Evaluating the technique of using nitrogen retention as a response criterion for amino acid studies in the horse. J Equine Vet Sci 2007; 27:525–30.
https://doi.org/10.1016/j.jevs.2007.10.012
85. Hackl S, van den Hoven R, Zickl M, Spona J, Zentek J. Individual differences and repeatability of post-prandial changes of plasma-free amino acids in young horses. J Vet Med A Physiol Pathol Clin Med 2006; 53:439–44.
https://doi.org/10.1111/j.1439-0442.2006.00862.x
87. Taylor YSM, Scrimshaw NS, Young VR. The relationship between serum urea levels and dietary nitrogen utilization in young men. Br J Nutr 1974; 32:407–11.
https://doi.org/10.1079/BJN19740092
92. Committee on Nutrient Requirements of Swine, National Research Council. Nutrient requirements of swine. 10th edWashington, DC, USA: National Academy Press; 1998.
93. Moehn S, Bertolo RF, Pencharz PB, Ball RO. Indicator amino acid oxidation responds rapidly to changes in lysine or protein intake in growing and adult pigs. J Nutr 2004; 134:836–41.
https://doi.org/10.1093/jn/134.4.836
94. Zhao XH, Wen ZM, Meredith CN, Matthews DE, Bier DM, Young VR. Threonine kinetics at graded threonine intakes in young men. Am J Clin Nutr 1986; 43:795–802.
https://doi.org/10.1093/ajcn/43.5.795
95. Brunton JA, Shoveller AK, Pencharz PB, Ball RO. The indicator amino acid oxidation method identified limiting amino acids in two parenteral nutrition solutions in neonatal piglets. J Nutr 2007; 137:1253–9.
https://doi.org/10.1093/jn/137.5.1253
96. Humayun MA, Elango R, Moehn S, Ball RO, Pencharz PB. Application of the indicator amino acid oxidation technique for the determination of metabolic availability of sulfur amino acids from casein versus soy protein isolate in adult men. J Nutr 2007; 137:1874–9.
https://doi.org/10.1093/jn/137.8.1874
97. Moehn S, Bertolo RF, Pencharz PB, Ball RO. Development of the indicator amino acid oxidation technique to determine the availability of amino acids from dietary protein in pigs. J Nutr 2005; 135:2866–70.
https://doi.org/10.1093/jn/135.12.2866
98. Mastellar SL, Coleman RJ, Urschel KL. Controlled trial of whole body protein synthesis and plasma amino acid concentrations in yearling horses fed graded amounts of lysine. Vet J 2016; 216:93–100.
https://doi.org/10.1016/j.tvjl.2016.07.007
99. Urschel KL, Geor RJ, Hanigan MD, Harris PA. Amino acid supplementation does not alter whole-body phenylalanine kinetics in Arabian geldings. J Nutr 2012; 142:461–9.
https://doi.org/10.3945/jn.111.149906