EFFECTS FEEDING OF GROWING STEERS ON PERFORMANCE, CARCASS CHARACTERISTICS, AND COMPOSITION

Two experiments were conducted to determine the effects of restricted feeding on performance, carcass characteristics, and composition. In T rial 1, 36 individually penned steer calves (280 +/- 13 kg BW) were fe d all-concentrate diets at intake levels of ad libitum and 90 and 80% of ad libitum. Trial 2 used 36 individually penned steer calves (298 /- 14 kg BW) fed corn silage-based growing diets for 84 d followed by 91% concentrate finishing diets. Intakes were as described for Trial 1 . Compared with steers with ad libitum intake, ADG was reduced (P <.00 5) .15 and .25 kg for steers fed 90 and 80% of ad libitum intake, resp ectively, in Trial 1. In Trial 2, growing phase ADG was reduced (P <.0 05) .15 and .24 kg for the 90 and 80% of ad libitum feed intake, respe ctively. Finishing phase ADG was reduced (P <.005) .12 and .21 kg for the 90 and 80% of ad libitum intake, respectively. Feed efficiency was not affected by intake when all-concentrate diets were fed in Trial 1 , or when a corn silage-based diet was fed in the growing phase of Tri al 2. During the finishing phase of Trial 2, feed efficiency was incre ased when intake was restricted. Carcass quality grade and 12th rib ba ckfat were reduced (P <.04) with decreases in daily feed intake when a ll-concentrate diets were fed. However, no effect on carcass character istics was observed in Trial 2. Liver and heart weights were not affec ted by daily feed intake. Serum triiodothyronine (T-3) concentrations tended (P =.11) to decrease for cattle receiving restricted intakes of all-concentrate diets and were decreased(P <.04) with intake restrict ion in Trial 2. Carcass fat content was reduced (P <.02), whereas carc ass protein and water were increased (P <.06) with reductions in daily feed intake in both trials. We concluded that restrictedly feeding gr owing-finishing steer calves does not decrease feed efficiency and act ually may improve feed efficiency. Restrictedly fed steers had reduced maintenance requirements, and lean tissue accretion represented a gre ater percentage of their total gain.