Figure 1.

Fitted quadratic polynomial (QP) and broken-line linear (BLL) regression models on feed efficiency (G:F) as a function of increasing standardized total tract digestible (STTD) P in 11- to 23-kg pigs in Exp. 1. The QP model estimated the maximum mean G:F at 0.42% (95% CI: [0.36, >0.53]%), with 99% of maximum G:F achieved at 0.36%. The estimated regression equation was G:F, g/kg = 456.59 + 1107.49 × (STTD P) − 1307.16 × (STTD P)². The BLL breakpoint was estimated at 0.34% (95% CI: [0.30, 0.37]%).The estimated regression equation was G:F, g/kg = 696.63 − 427.26 × (0.3358 − STTD P) if STTD P < 0.34%, and G:F, g/kg = 696.63 if STTD P ≥ 0.34%.