Fitted straight broken-line of weight gain as a function of SID-Lys:ME ratio (Exp. 4). Observed block mean values in each treatment (dot represent block 1, square represent block 2, triangle represent block 3, × represent block 4, plus represent block 5, DIAMOND represent block 6) are shown. The straight broken line: y = 0.6664 - 0.07787 × (3 - x) + LVAR (r2 = 0.76, adjusted r2 = 0.64). Parameter LVAR represents the block effect and produces different lines for the respective blocks. The optimum SID-Lys:ME ratio was 3 in 28 to 47 kg pig.