Effects of intake of monensin during the stocker phase and subsequent finishing phase on performance and carcass characteristics of finishing beef steers

Abstract

Use of monensin during the stocker phase of production has been suggested as a possible cause of reduced response to monensin during finishing. Experiments were conducted to determine the carryover effects of monensin supplementation during the stocker phase and effects of feeding monensin during the finishing phase on performance and efficiency of beef steers. Steers were fed hay or grazed cool-season annuals or bermudagrass in Arkansas before finishing in Canyon, Texas (blocks 1 and 2) or Stillwater, Oklahoma (block 3). Treatments were arranged as a 3 × 2 factorial with 3 monensin doses during the stocker phase (0, 882, or 1,764 g/t offered in a free-choice mineral) and 2 levels during finishing (0 or 37.5 mg/kg of diet DM). There were no block × treatment interactions ( P ≥ 0.19) for performance or carcass measurements; therefore, data were pooled across blocks and finishing locations. Stocker × finishing treatment interactions were not observed for finishing performance and efficiency data ( P ≥ 0.50). There was no carryover effect on overall finishing performance or efficiency. Cattle consuming monensin during the finishing phase had decreased ( P < 0.01) DMI during finishing and increased ( P < 0.01) G:F and ( P = 0.03) fat thickness compared with those not fed monensin during the finishing phase. Supplementation of monensin to stocker cattle before finishing did not affect subsequent finishing efficiency response to monensin during finishing. Providing monensin in finishing diets still decreases DMI and improves feed efficiency of finishing cattle.