Nursery pig ADG dose response curves dependent on standardized ileal digestible (SID) Lys. Broken-line linear Estimated breakpoint 1.45% SID Lys, [95% CI: (1.31, 1.58)]; BIC = 305.8. QP Estimated > 1.60% SID Lys that maximized ADG [95% CI: (1.47, > 1.60)]; 95% of Maximum: 1.43% SID Lys; BIC = 306.8. A total of 300 nursery pigs (PIC 327 × 1,050, initially 6.7 kg BW) were used in a 28-d growth trial with 5 pigs per pen and 10 pens per treatment. Pigs were weaned at approximately 21 d, fed a common starter diet for 6 d post-weaning, then fed dietary treatments. Quadratic polynomial (QP), broken-line linear (BLL), and broken-line quadratic (BLQ) models were fit to characterize the SID Lys dose response curve.