PERFORMANCE, DRY-MATTER INTAKE, DIGESTA KINETICS, AND RUMINAL FERMENTATION OF STEERS GRAZING SORGHUM-HALEPENSE AT 3 STOCKING RATES

A 2-yr study was conducted to evaluate performance, intake, digesta ki netics, and ruminal fermentation patterns of steers grazing Sorghum ha lepense (johnsongrass) at 3 stocking rates. Grazing lasted for 70 d in 1990 and 87 d in 1991. In 1990, stocking rate did not affect bodyweig ht gain, forage intake, quality of oesophageal masticate, or ruminal f ermentation patterns; however, increased stocking rate decreased parti culate and fluid dilution rates (22 and 37%, respectively), without af fecting dry matter fill or fluid volume. In 1991, increased stocking r ate decreased steer gains and total gain/ha, but did not affect qualit y of oesophageal masticate, intake or ruminal fermentation patterns. A s in 1990, increased stocking rate decreased particulate flow rate and tended to decrease ruminal fluid dilution rate. Increased stocking ra te also increased dry matter fill, but did not affect ruminal fluid vo lume. In 1990, quality of oesophageal masticate samples decreased from June through August, which was associated with decreased intake and r ates of passage, as well as altered ruminal fermentation patterns. In 1991, seasonal changes were less pronounced. Johnsongrass provided ste er average daily gains of up to 0.55 kg/d for 87 d with continuous sto cking. Stocking rate affected rates of particulate and fluid passage i n steers independent of changes in forage quality.