Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 25, 1996
Publication Date: N/A
Interpretive Summary: Eastern gamagrass is a warm-season, perennial grass with potential as a grazed forage, but intense grazing management is required for it to persist. A grazing study was conducted to evaluate forage quality and steer weight gains for eastern gamagrass stocked continuously with stocking rates of 3.0, 4.9, and 7.4 steers/ha. Grazing was terminated for each stocking rate once the pasture was grazed to a height of 30 to 38 cm; thus, the stocking rates provided short to long durations of continuous stocking as stocking went from heavy to light rates. The approximate number of days of grazing provided by each stocking rate was 90 days for the heavy rate, 120 days for the intermediate rate, and 140 days for the light rate. Crude protein and dry matter digestibility were initially high, but declined to marginal to low levels through the season. Similarly, steer average daily gain was initially high, but declined through the season. The reductions in average daily gain were similar among the three durations of continuous stocking. Gain per hectare increased over the season, but reached a maximum before termination of grazing. This was particularly true for the intermediate and long durations of continuous stocking where the durations were of long enough lengths to result in the steers grazing forage of low quality. Heavy stocking over a short duration produced the highest gain per hectare. Eastern gamagrass can produce high gains per hectare if grazed continuously with a high stocking rate over a duration of about three months before pastures are grazed to a height of 30 to 38 cm.
Technical Abstract: Eastern gamagrass [Tripsacum dactyloides (L.) L.] has potential as a grazed forage, but options in its grazing management should be evaluated. A grazing study was conducted to determine temporal effects on steer performance and nutritive values for eastern gamagrass that was continuously stocked for different durations of time. Pastures were stocked at three different rates and grazed to a 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); and 3) Short duration of grazing with a heavy stocking rate (7.4 steers/ha). The study was conducted for three years in a randomized complete block design with two replications. Crude protein percentage and IVOMD of both leaf blade and sheath showed nonlinear declines (P<.05) as days on pasture increased. Cumulative average daily gain declined linearly (P<.05) as days on pasture increased, but the relationships did not differ (P>.10) among durations of grazing or years. Cumulative liveweight gain showed a quadratic increase (P<.05) as days on pasture increased, but there also was an interaction (P<.001) on the linear term between duration of grazing and days on pasture. Cumulative liveweight gains for short-duration of grazing with a heavy stocking rate showed steep increases as days on pasture increased. For long and intermediate durations of grazing, liveweight gains stabilized in the late season. Results show that high liveweight gains can be achieved with continuously stocked eastern gamagrass if grazed with high stocking rates to a targeted pasture height of 30 to 38 cm.