Mineral Concentrations of Annual Cool Season Pasture Forages in North Florida during the Winter-Spring Grazing Season: II. Trace Minerals

Concentrations of selected trace minerals (Cu, Fe, Zn, Mn, Co, Se) were determined from annual cool-season grass pasture forages over four consecutive winter-spring grazing seasons (2001-2005). Twice monthly forage samples were taken from eight experimental pastures used in beef cattle grazing trials. Two, 2-yr experiments were conducted; animal and pasture data were reported previously. Each experiment was of a similar 2x2 design comparing clean-tilled vs. sod-seeded pastures with two annual forage combinations (Study 1, rye + oats vs. rye + oats + ryegrass; Study 2, oats + ryegrass vs. ryegrass only). Pastures were planted in Oct or Nov, and grazed (sampled) starting Nov, Dec, Jan or Feb and ending Apr or May. The overall mean concentrations of pasture forage for Exp. 1 and 2 respectively were (ppm of dry matter): Cu, 6.4 and 5.2; Fe, 88 and 68; Zn, 38 and 42; Mn, 105 and 114; Co, 0.06 and 0.06; and Se, 0.05 and 0.06. Year affected (P<0.05) forage Cu, Fe, Zn, and Se in Exp. 1 and Fe and Zn in Exp. 2. Pasture establishment method affected (P<0.05) Cu, Fe, Zn, and Mn in Exp. 1 and Mn and Se in Exp. 2. Forage treatment affected (P<0.05) Zn in Exp. 1 and Cu, Fe, Zn, Mn, and Co in Exp. 2. Sampling month affected (P<0.05) all minerals in both experiments except Cu and Zn in Exp. 2; monthly Se and Co were not evaluated due to limited analyses. Results indicate that forage type, pasture establishment method, year, and month of grazing season can affect concentrations of trace minerals of annual coolseason grass pasture forages in the southeastern USA.