The Effect Of Single and Multi-Species Grazing On Herbage Mass and Botanical Composition Of Permanent Grassland Following Winter Grazing.

The experiment was established at the WVU Reedsville Experimental Farm (Preston County, WV). The objective of this study was to compare the effect of single or mixed grazing during the growing season on herbage production and botanical composition of a sward used for winter grazing. Using a completely random design, three grazing treatments, with three repetitions were compared from 2009 to 2012, May 1^st to August 1^st each year.  The treatments were: TR1) Single species (2 steers), TR2) mixed I (1 steer + 6 lambs), and TR3) mixed II (2 steer + 2 lambs). Yearling Angus and Hereford crossbred steers and Suffolk crossbred, post-weaned lambs in TR2 and yearlings in TR3 were used. Animals grazed on 0.41 ha paddocks that included orchardgrass (Dactylis glomerata L.), Kentucky bluegrass (Poa pratensis L.), timothy (Phleum pratense L.), velvetgrass (Holcus lanatus L.) and other grasses, associated with white clover (Trifolium repens L.) and red clover (T. pratense L.) and forbs including creeping Charlie (Glechoma hederacea L.), dandelion (Taraxacum officinale Weber ex F. H. Wigg.), dock (Rumex crispus L.), horsenettle (Solanum carolinense L) and other forbs. Thirty sward heights for biomass estimation were taken weekly using a 0.2 m² plate meter, along three regularly spaced transects within each plot. Two 1m² exclusion cages were positioned in each pasture, 4 sward heights were measured at set up and each time cages were moved. Sward height was converted to herbage mass using an equation obtained by site specific calibration between 2004 and 2009. Two samples per cage were clipped at 2-week intervals, one inside the exclusion and one outside the cage. Samples were manually separated into grasses, legumes, forbs and senescent material (SM), and then dried at 60°C in a forced-draft oven. Proportion of grass, legumes, forbs and SM was determined by weight. Soil characteristics were similar between treatments. Average herbage mass during the grazing season for TR1 and TR2 was higher than for TR3 (2888, 2727 and 2343 kg.ha^-1 respectively; P<0.0001). No difference in herbage mass was observed in the late July measurements (2157, 1886 and 1974 kg.ha^-1) and available herbage did not restrict animal performance. Grazing with cattle alone (TR1) reduced the proportion of grass (P<0.017), and increased the proportion of legumes (P<0.0001) and forbs (P<0.056), no differences between treatments were found in SM. No differences were found between grazed and excluded areas for percentage of grass (P<0.448) and legume (P<0.109) but in the exclusion, the proportion of forbs was higher (P<0.025) and the proportion of SM was lower (P<0.028). Average daily gain for cattle ranged between 1.1 – 1.8 and for sheep 0.18 - 0.32 kg.d^-1.