Temporal effects on steer performance and nutritive values for eastern gamagrass grazed continuously for different durations.

Abstract

Eastern gamagrass (Tripsacum dactyloides [L.] L.) has potential as a grazed forage, but options in its grazing management need to be evaluated. A 3-yr grazing study was conducted to determine temporal effects on steer performance and nutritive values for eastern gamagrass that was continuously stocked for various durations. Pastures were stocked at different rates and grazed to targeted forage height of 30 to 38 cm to impose treatments of 1) long duration of continuous stocking with a light stocking rate (3.0 steers/ha) 2) intermediate duration of grazing with an intermediate stocking rate (4.9 steers/ha) or 3) short duration of grazing with a heavy stocking rate (SDHS; 7.4 steers/ha). Crude protein percentage and in vitro organic matter digestibility of leaf blade and sheath showed nonlinear declines (P < .05) as days on pasture (DOP) increased. In vitro organic matter digestibility of leaf sheaths was affected by two-way interactions (P < .05) between year and the linear, quadratic, and cubic terms. Crude protein percentage of leaf sheaths was affected by three-way interactions (P < .01) between duration of continuous stocking (DCS), year, and the linear and quadratic terms. There were linear declines (P < .05) of cumulative average daily gain as DOP increased, and the relationships did not differ (P > .10) among DCS or years. There was a quadratic (P < .05) relationship between cumulative live weight gain (kg/ha) and DOP, but there also was an interaction (P < .001) between DCS and DOP on the linear term. Cumulative live weight gains (kg/ha) for SDHS showed the steepest increases as DOP increased. High live weight gain per unit of land area can be achieved with eastern gamagrass, if grazed with high stocking rates to a targeted pasture height of 30 to 38 cm.