Sheep, classified as intermediate feeders, possess a narrow muzzle and a large rumen relative to body mass, allowing them to graze selectively and still tolerate substantial fiber content. Sheep, like all ruminants, have incisors only on the bottom with a hard dental pad in their upper jaw. Sheep also possess a relatively small mouth allowing them to graze relatively close to the ground and take small bites to select specific parts of a plant, such as small leaves or buds. These anatomical differences give them an advantage over cattle to harvest prostrate plants or strip leaves or flowers from stems. These features result in diets generally dominated by forbs. (Forbs are herbaceous plants that are not grasses, usually with broad leaves and showy flowers.) Indeed, sheep have been used successfully to control several weedy forbs including leafy spurge, spotted knapweed, yellow starthistle, thistles, tansy ragwort, and others.
Sheep will readily consume grass-dominated diets when grasses are succulent or when other forages are unavailable. Sheep tend to consume more forbs as forb availability increases. Plant parts that are tender, succulent, and readily visible are usually selected over those that are coarse, dry, and obscure. Compared with cattle, it is more difficult for sheep to graze tall dense stands of forage than short dense stands.
Sheep are small, sure-footed, and well suited for travel in rough topography. Sheep will graze steeper terrain than most cattle and tend to avoid marshy wet areas. These attributes, coupled with their gregarious nature, make them ideal for careful and strategic application of grazing in many weed-dominated lands.