The results of this study indicate that a 20% reduction of dietary CP, Lys, and other essential AA in comparison with conventional diets for finishing heavy pigs did not affect CW or BF, exerted trivial effects on the loin weight and yield, and did not affect the weights or yields of dressed hams and other primal cuts. In addition, the tested dietary reductions did not affect the uniformity of the carcasses or the weights of the main lean cuts. Barrows and gilts differed in several carcass traits, but dietary treatments generally did not interact with sex. Sire, which was the most important source of variation for the investigated carcass traits, interacted with the dietary treatment for CW, but not for the proportion of lean or fat cuts on CW. These results indicate that in the traditional heavy pig production system aimed at producing DPO dry-cured hams, diets containing 117 or 108 g CP/kg and 5.8 or 4.6 g total Lys/kg for the BW ranges of 90 to 130 or 130 to 165 kg, respectively, can be applied regardless of the gender or the genetic merit of sires, at least within the pig line studied herein. The use of such low-protein diets would reduce N emissions from pigs operations and decrease feeding costs without impairing carcass quality or uniformity.