Wednesday, November 15, 2006

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

Gunasegaran Chelliah, Robert Myer, Jeffrey Carter, and Lee McDowell. University Of Florida, "Nfrec, 3925 Highway 71", Marianna, FL 32446, United States of America

Concentrations of selected trace minerals (Cu, Fe, Zn, Mn, Co, Se) were determined from annual pasture forages over four consecutive winter-spring grazing seasons (2001-2005).  Twice monthly forage samples were taken from 8 experimental pastures used in beef cattle grazing trials.  Two, 2 yr studies were done; animal and pasture data were reported previously.  Each study was of a similar 2x2 design comparing 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 (range) for Study 1 and 2, respectively were (ppm of DM): Cu, 6.4 (4.0 to 9.9) and 5.2 (4.0 to 9.4); Fe, 88 (56 to 242) and 68 (30 to 156); Zn, 38 (13 to 56) and 42 (29 to 74); Mn, 105 (56 to 171) and 114 (62 to 160); Co, 0.06 (0.02 to 0.10) and 0.06 (0.03 to 0.12); and Se, 0.50 (0.03 to 0.07) and 0.06 (0.04 to 0.08).  Year affected (P<0.05) Cu, Fe, Zn and Se in Study 1 and Fe and Zn in Study 2.  Pasture planting method affected (P<0.05) Cu, Fe, Zn and Mn in Study 1 and Mn and Se in Study 2. Forage treatment affected (P<0.05) Zn in Study 1 and Cu, Fe, Zn, Mn and Se in Study 2.  Sampling month affected (P<0.05) all minerals in both studies except Mn in Study 1.  Results indicate that forage type, pasture planting method, year and especially month within year can affect concentrations of trace minerals of annual cool season pastures in the southeastern USA.