Non-destructive assessment of cattle forage selection: A test of skim grazing in fescue grassland

Abstract

This study evaluated a non-destructive scientific method that is non-invasive to the animal, for quantifying foraging selectivity by cattle within heterogeneous pasture swards in order to test the utility of a new grazing system designed to aid conservation of native rough fescue ( Festuca campestris Rydb.) rangeland in western Canada. Skim grazing is a recently developed strategy that involves a light, once-over-spring defoliation, followed by a late to dormant season grazing period. This practice is thought to conserve rough fescue as cattle are assumed to prefer invasive grass species during spring when fescue is sensitive to defoliation. We examined the preferences of cattle for each of four major grass species, two native and two introduced, within rough fescue rangeland, grazing during spring, fall, or spring and fall of 2000 and 2001. We developed height–biomass models for each grass species in each grazing period, determined biomass removal by species, and despite under-estimating actual herbage removal, successfully evaluated cattle preferences. Though the interpretation of established preferences are limited to the conditions of this study, rough fescue together with the introduced species, Kentucky bluegrass ( Poa pratensis L.), were preferred during spring, contrary to our hypothesis. Kentucky bluegrass was also preferred within both fall and fall regrowth pastures. Smooth brome ( Bromus inermis Leyss.) and Parry oat grass ( Danthonia parryii Scribn.) were generally avoided. The failure of cattle to avoid rough fescue during spring indicates skim grazing may negatively impact the conservation of rough fescue grassland. In contrast, fall grazing appears conducive to sustaining fescue grasslands while capitalizing on forage production from invasive species like Kentucky bluegrass.