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Two experiments were conducted to determine the efficiency of utilization of crystalline lysine relative to the lysine in soybean meal for growth in barrows and gilts fed individually or in groups. One hundred twelve growing pigs (56 barrows and 56 gilts; average initial body weight of 39.6 lb) were sued in each experiment. Pigs were fed individually (I) or in groups of three (G). There were 28 individually penned and 84 in 28 pens with three pigs/pen). There were two replications per treatment in each experiment for a total of four replications. For the 28-day experiments, pigs were fed one of seven dietary treatments in both experiments. Dietary treatments consisted of a basal diet (0.55% lysine) and diets containing 0.65, 0.75, and 0.85% lysine that were achieved by adding lysine to the basal diet from either soybean meal (SBM) or L-lysine•HCl (crystalline). Average daily (ADG), average daily feed intake (ADFI), and feed efficiency (ADG/ADFI) were recorded. Total lysine intake (TLI) and supplemental lysine intake (SLI) were calculated. At the end of the experiments, all pigs were scanned using real-0time ultrasound to determine tenth-rib backfat depth and longissimus muscle area (LMA) to calculate fat-free lean gain (FFLG). Blood samples were taken from all pigs weekly to determine plasma urea concentration (PUC). Growth performance was similar between pigs fed crystalline lysine or SBM. Average daily gain was affected by dietary lysine concentration (P<0.01) but was similar for both sources of lysine. Pigs fed individually had a greater ADG than pigs fed in groups (P<0.05). No differences among dietary treatments (P>0.10) were observed in ADFI. However, pigs fed individually had a greater ADFI (P<0.05) than pigs fed in groups. Feed efficiency improved as the lysine concentration in the diet increased (P<0.01). Backfat depth was similar among treatments (P>0.10), and LMA increased (P<0.01) as the lysine concentration increased for both sources of lysine. Gilts had a greater LMA (P<0.01) than barrows. Fat-free lean gain increased (P<0.02 as dietary lysine concentration increased regardless of lysine source. Gilts were leaner than barrows (P<0.01). Total lysine intake increased with increasing dietary lysine in both sources of lysine (P<0.01). Pigs that were fed individually consumed more total lysine than pigs fed in groups (P<0.05). Pigs fed individually recievign the diet supplemented with 0.30% lysine from the crystalline source consumed 0.30 g/d less than pigs fed the diet supplemented with the same amount of lysine from SBM (P<0.10). There was a diet x week interaction (P<0.01) for PUC. The PUC decreased for pigs consuming crystalline-supplemented diets and increased for pigs consuming SBM-supplemented diets during the 4-wk experimental period. The results indicate no significant differences in growth performance and carcass traits of pigs fed supplemented diets from L-lysine•HCl and soybean meal, suggesting that the efficiency of lysine utilization from SBM-bound lysine is similar to crystalline lysine.