Comparison of three weaning ages on cow-calf performance and steer carcasstraits

An experiment was conducted to compare three weaning ages on cow-calf perfo rmance and steer carcass traits. Crossbred steers (n = 168; 1/2 Simmental x 1/4 Angus x 1/4 Hereford) were randomly assigned to three treatments with eight pens per treatment: groups were 1) weaned at an average of 90 d of ag e (90 +/- 13 a) and placed in the feedlot, 2) weaned at an average of 152 d of age (152 +/- 13 d) and placed in the feedlot, and 3) weaned at an avera ge of 215 d of age (215 +/- 13 d) and placed in the feedlot. The number of days steers were finished decreased by 55 and 38 d (linear, P = .0001) as w eaning age increased when slaughtered at a constant fat end point (.81 cm). Weaning at an average of 90 and 152 d of age improved overall ADG by .15 a nd .07 kg/d, respectively, over weaning at an average of 215 d of age (line ar, P = .005). Over the entire finishing period, intake increased (linear, P = .0006) and efficiency was poorer (linear, P =.004) as weaning age incre ased. Owing to differences in finishing days and intake, total concentrate consumed increased (linear, P = .03) as weaning age decreased. No differenc es (P > .21) were observed for carcass weight, longissimus muscle area, or yield grade. No differences (P > .19) were observed in marbling score or pe rcentage of steers grading greater than or equal to Choice or Average Choic e. Cow body condition score improved (linear, P = .0001) as weaning age dec reased. Pregnancy rate improved 12 percentage units (linear, P = .15) for c ows on the 90-d weaning treatment. In this study, early weaning improved ga in and feed efficiency, but it increased total concentrate consumed.