Reciprocal recurrent selection in swine: carcass traits [Heterosis]

Selection involving six cycles of reciprocal recurrent selection (RRS) was conducted over a period of 12 yr, followed by a 4-yr evaluation phase. Selection in two unrelated selected strains was based on an index of sow productivity for preweaning litter traits in the parental strains and on postweaning gain, carcass backfat thickness and yield of five preferred cuts (percentage PC) in their reciprocal strain-cross progeny. In addition, concurrent selection in two control strains derived from the same base populations was limited to the dam's preweaning litter productivity.