Evaluating Texel-, Suffolk-, and Columbia-Sired Offspring: II. Postweaning Growth and Carcass Traits Under Feedlot and Pasture-Feedlot Finishing Systems

A terminal sire study was conducted to evaluate postweaning growth and carcass traits of Texel-sired offspring compared with Suffolk- and Columbia-sired offspring. The lambs were weaned at an average age of 70 and 94 d during the 2-yr study, respectively. After weaning, lambs from each sire breed were allocated to one of two finishing programs. Finishing programs were 1) direct to feedlot ( FP1 ) and 2) pasture followed by feedlot ( FP2 ). In the feedlot, lambs were fed ad libitum shelled corn (74.86% TDN and 7.18% CP, as fed) and pelleted protein supplement (43.20% CP) in a ratio of 85:15, respectively. Lambs were harvested at a BW of 58.5 kg (±7.2 kg). The ADG was greatest for Suffolksired offspring, followed by Columbiaand Texel-sired offspring (318, 286, and 262 g, respectively; P<0.01). Mean ADG was greater (P<0.01) for FP1 lambs than for FP2 lambs (333 vs 244 g, respectively). Feed efficiency (FE) in drylot was similar for offspring of each sire breed; however, FE was greater for FP1 than for FP2 (4.4 vs 5.1 kg of DMI/kg of BW gain, respectively; P<0.05). Texel-sired carcasses had greater (P<0.01) longissimus area ( LA ) than Suffolk- and Columbia-sired carcasses (17.3, 16.1, and 16.1 cm2, respectively). Texel- and Suffolk-crossbred lambs were similar to Columbiacrossbred lambs in backfat ( BF ) thickness (0.79, 0.61, and 0.70 cm, respectively), although BF thickness was greater (P<0.05) in Texel- than Suffolkcrossbred lambs. Body wall thickness ( BWT ) was less (P<0.10) in Texel- and Suffolk-sired carcasses than in Columbia-sired carcasses (2.95, 2.99, and 3.21 cm, respectively). Dressing percentage ( DP ) and quality grades were similar for lambs from the 3 sire breeds. Lambs finished on FP2 had more LA (P=0.05) and less BF (P=0.10) than lambs finished on FP1 (16.4 vs 15.5 cm 2 and 0.54 vs 0.64 cm, respectively). The BWT was also less in carcasses of lambs finished on FP2 vs FP1 (2.57 vs 2.85 cm, respectively; P<0.01). The interactions between sire breeds and finishing programs were nonsignificant for all growth and carcass traits except DP. These data indicate that Texel-sired crossbred lambs may have some potential for increasing muscle mass. However, increased lean mass of Texel-crossbred lambs is counterbalanced by lesser postweaning growth rate than Suffolk- and Columbia-sired crossbred lambs. Grazing lambs following weaning and prior to finishing in drylot improved leanness and muscling without influencing quality grade.