A total of 2,121 growing-finishing pigs (Duroc × Landrace × Large White) were utilized in six experiments conducted to determine the effects of different ratios of standardized ileal digestible lysine (SID-Lys) to metabolizable energy (ME) on the performance and carcass characteristics of growing-finishing pigs. In the first three experiments, graded levels of energy were fed to determine an optimum ME level for each weight group and three experiments were to test the response of pigs to different ratios of SID-Lys:ME. In one of three experiments, weight gain was significantly increased with increasing energy level. For all three experiments, feed intake was decreased (P < 0.05); feed efficiency was improved (P < 0.05); and tenth rib back fat thickness linearly increased (P < 0.05) with increasing energy level.

In three experiments comparing SID-Lys:ME ratios, weight gain were increased (P < 0.05); feed efficiency was improved linearly (P < 0.05); and tenth rib back fat thickness linearly decreased (P < 0.05) as the SID-Lys:ME ratio increased. Based on these experiments, the estimated SID-Lys:ME ratio to maximize weight gain was 3.0, 2.43 and 2.2 for 29-47, 54-76 and 84-109 kg of pigs, respectively.