Add to ORKGAn experiment was conducted to evaluate the effects of dietary protein concentration on growth performance, plasma urea concentration, liver weight and liver arginase activity of finishing (138 lb) barrows and gilts. Average daily feed intake, arginase activity and plasma urea concentration were greater in barrows than in gilts, whereas liver weight was lighter in barrows than in gilts. These data suggest gilts are affected more negatively by high protein diets than barrows. We believe the changes in liver weight and urea cycle enzymes (arginase) are related to these feed intake differences