GRAIN SUPPLEMENTATION ON BLUESTEM RANGE FOR INTENSIVE-EARLY STOCKED STEERS

A 4-year study was conducted on Kansas Flint Hills bluestem range to m onitor animal gain, grass, and forb standing biomass following grazing , plant population dynamics, and in 2 years, subsequent feedlot perfor mance of steers under intensive-early stocking supplemented with incre asing levels of sorghum grain. Each year from 1988 through 1991, cross bred beef steers were stocked at 0.24 ha/100 kg of initial steer weigh t from 5 May to 15 July. Steers in twice-replicated pastures were give n no supplementation, 0.91 kg rolled sorghum grain per head daily, or 1.82 kg rolled sorghum grain per head daily, which corresponded to app roximately 0, 0.3, and 0.6 of body weight(-1). All steers were implant ed with estradiol 17 beta in 1988 and zeranol in 1989-91 during initia l processing and had unlimited access to a lasalocid/mineral mixture d uring the entire trial. In 1989 and 1990, representative groups of ste ers selected from all treatment/pasture combinations were subjected to a feedlot finishing phase and carcass data were obtained. Grass and f orb standing crops were estimated each year at livestock removal in mi d-July and again in early October. Pretreatment species composition an d basal cover were determined in 1988 and compared to those at the end of the study. In mid-July, when cattle mere removed, residual standin g biomass of grass increased in direct proportion to increasing level of supplement. Standing biomass of grass at the end of the growing sea son did not differ among pastures with different supplement levels, Fo rb standing biomass did not differ among pastures with different suppl ement levels in July or October. Changes in plant populations among tr eatments during the course of the study were minimal. During the early portion of the grazing period, sorghum grain supplementation did not significantly influence steer gains, but average daily gain during the latter part of the grazing period increased in direct proportion to i ncreasing level of sorghum grain supplement. Daily gain, feed intake, carcass characteristics, and gain:feed ratio were not different among treatments during the feedlot phase. Although conversion efficiencies may be economically marginal, low-level grain supplementation has the potential to increase the daily gain of tattle grazing early-season ta llgrass prairie under an intensive-early stocking program.