145 Effects of Increasing Dietary Standardized Ileal Digestible Lysine Levels on Growth Performance of 12- to 23-Kg Boars and Gilts

Abstract

Abstract Our objective was to determine the effects of increasing dietary standardized ileal digestible (SID) lysine (Lys) on growth performance of late nursery boars and gilts. A total of 1,920 pigs (PIC 337×Camborough, initially 12.1±1.34kg) were used in a 21-d trial. Pens of pigs were weighed, blocked by body weight, and randomly allotted to 1 of 5 treatments containing 1.10, 1.16, 1.29, 1.42, and 1.48% SID Lys (corresponding to 85, 90, 100, 110 and 115.0% of PIC SID Lys recommendations). Diets were corn-soybean-meal-based and contained 3,300 Kcal of ME/kg. There were 6 split gender pens/treatment and 32 pigs/pen. Data were analyzed using generalized linear and nonlinear mixed models with pen as the experimental unit. Competing models included linear, quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ). There was no evidence of linear or quadratic SID Lys concentration by gender interaction. Increasing SID Lys concentration improved average daily gain (ADG; quadratic, P < 0.05) and gain to feed ratio (G:F; quadratic, < 0.01). The QP, BLL, and BLQ had similar fit for the ADG and G:F. In the QP model, 95% and 100% of the ADG were at 1.18 and 1.36% of SID Lys, respectively, and 1.17 and 1.35% for G:F. The BLL and BLQ models estimated the breakpoint at 1.20% (95% CI: 1.06-1.35%) and 1.22% SID Lys (95% CI: 0.97-1.47%), for ADG, respectively. For G:F, the BLL and BLQ models estimated the breakpoint at dietary SID Lys of 1.20% (95% CI: 1.07-1.33%) and 1.20% (95% CI: 1.03-1.38%), respectively. There was no evidence that increasing dietary SID Lys levels impacted average daily feed intake or the removal and mortality rate. In the current trial with dietary ME level at 3,300 kcal/kg, the estimated optimum SID Lys concentration for 12- to 23-kg boars and gilts ranged from 1.20-1.36%, depending on the statistical model.