The effect of breed and individual heterosis on the feed efficiency, performance, and carcass characteristics of feedlot steers.

This study was conducted to evaluate maternal breed effects, direct breed effects, and individual heterosis on subsequent steer performance, carcass, and feed efficiency traits. This was a consecutive 2-yr trial using 158 steers. The same dam breeds, Angus (AN) and purebred Simmental (SM), were used both years. Also, the same AN and SM sires (n=11) were used both years. Steers were AN, SM, or AN×SM breed composition. Steers were managed similarly before weaning and early weaned at 56±9 d of age. Steers were then randomly allotted to pens and fed a common finishing ration. Contrasts were written to evaluate direct and maternal breed effects and individual heterosis in the PROC MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) using dam breed, sire breed, and year as fixed effects. Simmental direct breed effect resulted in a 26 kg heavier initial BW (P<0.05) and a 46 kg heavier final BW (P<0.05). Simmental maternal breed effect increased initial BW by 43.5 kg (P<0.05). Dry matter intake was not impacted by direct breed effects, maternal breed effects, or individual heterosis. Individual heterosis did improve G:F 3.4% (P<0.05) and residual BW gain 0.048 kg/d (P<0.05). Residual intake and BW gain tended (P=0.07) to improve as a result of individual heterosis. Residual feed intake (RFI) was impacted by direct breed effect with SM cattle having a more desirable RFI (P=0.05). Angus direct breed effect increased backfat (P<0.05) and improved marbling score by 126 units (P<0.05). Simmental direct breed effect increased LM area (P<0.05), had the highest HCW at 410 kg (P<0.05), and had the most desirable yield grade at 2.74 (P<0.05). Individual heterosis improved marbling score (P=0.05). Maternal breed effect increased HCW (P<0.05) as a result of the SM dam. Direct breed effects were present for performance, feed efficiency measures, and carcass traits. Overall, heterosis impacted feedlot performance, carcass characteristics, and feed efficiency, which impacts beef production.