Abstract: Grazing represents a sustainable alternative for the control of medusahead infestations but intake of medusahead by ruminants is typically low. We determined in sheep whether 1) high-energy supplements enhance medusahead intake and preference relative to a treatment without supplementation and 2) individual differences in medusahead intake transfer to individual differences in the ingestion of a silica-containing ration. Groups of lambs (n=10) were individually penned and randomly assigned to 3 supplementation treatments: 1) Control; no supplement; 2) beet pulp:barley:calcium (Ca) propionate; 67:30:3 , or 3) beet pulp:barley:yeast culture; 65:30:5. After supplementation, all animals had ad libitum access to medusahead in late vegetative to mid-reproductive (Trial 1), and late-reproductive phenological stages (Trial 2). Medusahead preferences were assessed by offering sheep a choice between medusahead and tall fescue hay. Plant part preferences were assessed by offering a choice between medusahead tops (mostly seedheads and awns) and mid-plant parts (mostly stems+leaves). Intake of medusahead was low and cyclic, declining towards the end of each trial (P < 0.0001) and there were no treatment differences (P > 0.10). Lambs preferred tall fescue hay to medusahead and medusahead tops to mid-plant parts (P < 0.0001). Supplemented lambs gained more weight than Control lambs (P < 0.10). Thus, supplemented lambs performed better than non-supplemented controls without reducing their intake of medusahead. In Trial 3, two new groups of lambs were formed based on their intake of medusahead during Trials 1 and 2 (n=10). One group consistently ate more medusahead and more of a ration containing silica (alfalfa:silica, 97:3) than the other (P < 0.10). A significant and consistent degree of individual variation was measured among lambs -irrespective of treatment- regarding their ability to ingest medusahead and silica. This variation represents a promising option for maximizing use of medusahead by livestock in rangelands. [Juan Villalba and Elizabeth Burritt (2015). Intake of Medusahead by sheep: Influence of supplements, silica and individual animal variation. Invasive Plant Science and Management, In-Press.] ${imageDescription} Comment