Browsing for conservation: springtime forage value of midstory shrubs of degraded oak savannas in southern Wisconsin.

摘要

Oak (Quercus spp.) savanna is a rare and dwindling ecosystem primarily due to the clearing of vast areas for agriculture and encroachment of woody midstory shrubs in the remnant areas. There is interest in introducing controlled grazing to re-open these ecologically sensitive semi-wooded areas. We report the forage quality and diet selection by Scottish Highland cattle (Bos taurus spp.), a breed recognized for their browsing behavior, of the most common shrubs in this ecosystem. Shrub species sampled included prickly ash (Xanthoxylem americana Mill), gooseberry (Ribes missouriense Nutt.), gray dogwood (Cornus racemesa L.), multiflora rose (Rosa multiflora Thunb. ex Murr.), black or red raspberry (Rubus spp.) and wild parsnip (Pastinaca sativa L). Leaf biomass was collected in June 2001 and 2002 and analyzed for forage quality. Animal observations showed that diet included a fairly even mixture of shrub leaves, grass and herbaceous forbs. Prickly ash and raspberry were most frequently browsed and had the highest crude protein (CP; 190 g kg-1), while multiflora rose and gray dogwood, neither highly browsed upon, had the lowest levels of CP (120 g kg-1). All shrubs had high in-vitro true digestibility, with prickly ash approaching 850 g kg-1 (as compared to 688 g kg-1 for mature alfalfa). The quality of the shrub layer in late spring is adequate to provide nutritional support for beef cattle as long as dry matter intake is not limited. Integrating shrubs into the rotation could expand the pasture base by providing feed at a time when cool-season pastures are typically quasi-dormant.