Diet selection by deer: principles, practice and consequences

Abstract

The role of diet selection by farmed deer in their nutrient intake and species selection, and the consequences for the management of forages, is considered. In common with sheep and cattle, sward surface height (SSH) is the most influential sward physical factor on the ability of deer to meet their daily nutrient demand from grazed pasture, and a SSH of 10cm is required for maximum intake and performance. Deer discriminate among pasture species, generally preferring legumes and herbs to grasses. The grass dominance and low proportion of clover in typical permanent pasture grazed by deer reflects their selection for clover and avoidance of grass. This dominance of grass and the difficulty deer face in selecting for alternative species that are present only in a low proportion may constrain intake even when sward height is not limiting. Summer-growing forage species such as red clover (Trif olium pratense), white clover (Tri folium repens), birdsfoot trefoil (Lotus corniculatus), sulla (Hedysarum coronarium) and chicory (Cichorium intybus) have high nutritive value, and result in high liveweight gains by deer when provided as specialist swards at critical feeding times. Recent studies indicate that ruminants prefer to eat mixed diets, and management systems that enable mixed grass-clover pastures with a high proportion of legume to be sustained under selective grazing by deer would provide high nutritive value and maintain a balance between winter and summer in the seasonal distribution of pasture dry matter production. Keywords: Cervidae, deer, diet selection, forage, grazing behaviour, nutrient intake, preference