HERBAGE CHARACTERISTICS AND PERFORMANCE OF STEERS GRAZING OLD-WORLD BLUESTEM

Old World bluestem (OWB; Bothriocloa spp,)are popular in the southern Great Plains but little is known about the relationships between forag e characteristics and animal productivity. The influence of difference s in herbage mass and sward height of OWE on rate of gain during the s ummer grazing season was examined during 2 years at El Reno, Okla, Soi ls were fine, silty Pachic Haplustolls of the Dale series. Swards of c aucasian [B, caucasica (Trin,) C, E, Hubb,] and 'Plains' [B, ischaemum var ischaemum (L,) Keng,] OWE were maintained at different levels of forage mass (low, medium, and high) by continuous variable stocking an d were grazed from mid- May to late September by steers with an initia l weight of about 225 kg, Weight gains were depressed in late August, but in 1985 gains recovered due to late season rains. Season-long gain s averaged 0.61 kg day(-1) in 1984 and 0.69 kg day(-1) in 1985, Daily gains of steers increased linearly with increased herbage mass (P < 0. 05), but slopes were different due to a year X species interaction. Da ily gains peaked at a herbage height of 41 cm in 1984, but increased l inearly throughout the range of the data (75 cm) in 1985, Individual a nimal gains decreased linearly with increasing stocking rate such that maximum gain per hectare was achieved at about 5 animals ha(-1) (stan dard 500 kg), The data suggest that maintaining higher herbage mass an d height of OWE forage improves animal performance and support the pra ctice of intensive early grazing and removing cattle by late July when rate of gain declines.