242 Effects of Standardized Ileal Digestible Threonine to Lysine Ratio on Growth Performance of PIC Line 337-Sired Grow-Finish Pigs

• Published in: Journal of animal science Vol. 101; no. Supplement_2; pp. 107 - 108
• Main Authors: Royall, Rafe Q, Tokach, Mike D, Woodworth, Jason C, DeRouchey, Joel M, Goodband, Robert D, Gebhardt, Jordan T, Vier, Carine M, Spindler, Matthew, Orlando, Uislei A, Zaragoza, Luis E, Lu, Ning, Cast, Wayne R, Wilson-Wells, Danielle, Holen, Julia, Betlach, Alyssa
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 01.11.2023
• Subjects: Body weight; Feed conversion; Feed conversion efficiency; Feed efficiency; Lysine; Polynomials; Soybeans; Swine; Threonine; requirement; amino acid; grow-finish pig; threonine
• ISSN: 0021-8812; 1525-3163
• DOI: 10.1093/jas/skad341.119

Abstract Two studies were conducted to estimate the SID Thr:Lys requirement for growth and feed efficiency of PIC 337×1050 pigs from approximately 12- to 70-kg. In Exp. 1, 987 pigs [initial body weight (BW) = 11.8±0.32 kg] were used from 12- to 24-kg. In Exp. 2,875 pigs (initial BW = 43.4±0.58 kg] were used from 43- to 70-kg. Pens of pigs were blocked by BW and randomly allotted to dietary treatments in randomized complete block designs, with 21 to 27 pigs per pen with 8 and 7 replications per treatment (Exp. 1 and 2, respectively). Pens were provided 1 of 5 dietary treatments with increasing SID Thr:Lys ratios at 53, 58, 62, 65, and 68% in each experiment. Two corn-soybean meal-based diets containing 53 and 68% Thr:Lys ratios were blended to achieve target SID Thr:Lys treatment levels in each experiment. In Exp. 1 (12- to 24-kg), ADG and final BW increased (linear, P ≤ 0.006) while ADFI, G:F, Thr intake/d, and Thr intake/kg of gain increased (quadratic, P ≤ 0.001) as Thr:Lys ratio increased (Table). Additionally, Lys intake/d increased (quadratic, P < 0.001) while Lys intake/kg of gain decreased (quadratic, P < 0.001) with increasing Thr:Lys ratio. In Exp. 2 (43- to 70-kg), ADG, G:F, final BW, Thr intake/d and Thr intake/kg of gain also increased (linear, P ≤ 0.036) as dietary Thr:Lys increased. Moreover, Lys intake/kg of gain decreased (linear, P = 0.023) with increasing Thr:Lys. A quadratic polynomial (QP) model predicted a requirement at levels greater than 68% SID Thr:Lys for ADG from 12- to 24-kg, while a QP model suggested that maximum G:F was achieved at 61.8% SID Thr:Lys (Exp. 1). From 43- to 70-kg, QP models suggested maximum ADG and G:F were achieved at levels greater than 68% SID Thr:Lys (Exp. 2). However, similar fitting BLL models predicted no further improvement to G:F and ADG beyond 65 and 67% SID Thr:Lys, respectively. In summary, these results suggest the optimal SID Thr:Lys for 12- to 24-kg pigs is 61.8% for feed efficiency and greater than 68% for ADG. From 43- to 70-kg, the requirement was predicted at or above 65 and 67% SID Thr:Lys for G:F and ADG, respectively.