title: Determining the optimal isoleucine:lysine ratio for ten- to twenty-two-kilogram and twenty-four- to thirty-nine-kilogram pigs fed diets containing nonexcess levels of leucine.
abstract: Three 21-d experiments were conducted to determine the optimum standardized ileal digestible (SID) Ile:Lys ratio in 10- to 22-kg and 24- to 39-kg pigs. In Exp. 1, 144 Yorkshire pigs (initial BW = 10.2 kg) were assigned to 6 diets with 6 pens per treatment. Diets 1 to 5 were formulated to contain 5 graded SID Ile:Lys (44, 51, 57, 63, and 70%), 1.18% SID Leu, and 0.90% SID Lys (second limiting). Diet 6 (diet 5 with added Lys) was formulated (1.06% SID Lys) as a positive control. Pigs fed diet 6 had higher (P < 0.05) ADG and G:F and lower (P < 0.05) plasma urea N (PUN) than pigs fed diet 5 (P < 0.02), indicating that Lys was limiting in diets 1 to 5. Final BW, ADG, and ADFI increased (linear and quadratic, P < 0.05) while G:F and PUN at d 21 were not affected (P > 0.10) by dietary Ile:Lys. Overall, ADG and ADFI were highest for pigs fed diet 2 (51% SID Ile:Lys). In Exp. 2, 216 Yorkshire pigs (initial BW = 9.6 kg) were assigned to 9 diets with 6 pens per treatment. Diets 1 to 4 contained 0.40, 0.47, 0.54, and 0.61% SID Ile, respectively, and 1.21% SID Lys; diets 5 to 8 contained 0.72, 0.84, 0.96, and 1.08% SID Lys, respectively, and 0.68% SID Ile. Diet 9 was high in both Ile and Lys (0.68% SID Ile and 1.21% SID Lys). All diets contained 1.21% SID Leu. The ADG and G:F increased (linear and quadratic, P < 0.05) as SID Ile:Lys increased (diets 1 to 4 and 9). The ADG and G:F increased (linear, P < 0.05) as SID Lys increased (diets 5 to 9). The PUN at d 21 decreased (linear, P < 0.05) by increasing dietary Ile:Lys. The SID Ile:Lys to optimize ADG was 46% by curvilinear plateau or exponential regression. For G:F, the optimal SID Ile:Lys was 47 and 51% by curvilinear plateau and exponential regressions, respectively. In Exp. 3, 80 pigs (PIC 327 × C23; initial BW = 24.0 kg) were allotted to 5 treatments with 4 pigs per pen. Diets 1 to 5 were formulated to contain 5 graded SID Ile:Lys (39, 46, 53, 61, and 68%), 1.17% SID Leu, and 0.91% SID Lys (second limiting). Final BW and ADG increased (linear and quadratic, P < 0.05) and ADFI increased (linear, P = 0.047) as SID Ile:Lys increased. Using ADG and G:F, the optimum SID Ile:Lys was 54 and 53%, respectively, by curvilinear plateau and exponential regression. The PUN was minimized at 53 and 59% SID Ile:Lys by curvilinear plateau and broken line regression. Overall, the average optimum SID Ile:Lys was approximately 51% for 10- to 22-kg pigs and 54% for 24- to 39-kg pigs fed diets containing nonexcess levels of Leu.
authors.affiliation: Evonik Industries AG, Rodenbacher Chaussee 4, 63457 Hanau, Germany john.htoo@evonik.com.
authors.forename: J K
authors.initials: JK
authors.lastname: Htoo
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: C L
authors.initials: CL
authors.lastname: Zhu
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: L
authors.initials: L
authors.lastname: Huber
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: C F M
authors.initials: CF
authors.lastname: de Lange
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington 40546-0215.
authors.forename: A D
authors.initials: AD
authors.lastname: Quant
authors.affiliation: USDA-ARS-National Laboratory for Agriculture and the Environment, Ames, IA 50011-3310.
authors.forename: B J
authors.initials: BJ
authors.lastname: Kerr
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington 40546-0215.
authors.forename: G L
authors.initials: GL
authors.lastname: Cromwell
authors.affiliation: Department of Animal and Food Sciences, University of Kentucky, Lexington 40546-0215.
authors.forename: M D
authors.initials: MD
authors.lastname: Lindemann
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001806:Blood Urea Nitrogen; D001835:Body Weight; D004032:Diet / Q000662:veterinary*; D004063:Digestion / Q000502:physiology*; D007082:Ileum / Q000502:physiology; D007532:Isoleucine / Q000502:physiology*; D007930:Leucine / Q000008:administration & dosage; D008239:Lysine / Q000502:physiology*; D009751:Nutritional Requirements / Q000502:physiology*; D012044:Regression Analysis; D034421:Sus scrofa / Q000254:growth & development*; D013552:Swine
chemical_list: D007532:Isoleucine; D007930:Leucine; D008239:Lysine
keywords: isoleucine; leucine; lysine; performance; pigs; ratio