From Invasive Bramble to Functional Browse: A Translational Review of Rubus ulmifolius Schott for Sheep Nutrition

Rubus ulmifolius Schott is an invasive bramble whose recurrently removed biomass may contain nutritionally useful leaves and young shoots. This narrative and translational review evaluates whether that biomass can be investigated as a candidate sheep supplement without encouraging its spread. Species-specific evidence shows marked seasonal and fraction-dependent variation in crude protein, fiber, lignin and tannin activity, whereas controlled sheep-feeding data remain scarce. Goat browsing observations and general studies of tannin-rich feeds support only indirect hypotheses regarding intake, rumen nitrogen metabolism, methane, microbiome composition, oxidative status, product quality and parasite resilience. Key constraints include mature-cane lignification, thorns and selective refusal, uncertain dose-response, processing effects, contamination and propagule biosecurity. We therefore define functional browse as an unvalidated, outcome-dependent designation and propose a staged evidence pathway: local biomass mapping and no-spread harvest; fraction-specific chemical and phytochemical characterization; in vitro digestibility, polyethylene-glycol and methane screening; short-term sheep acceptability and safety; controlled dose-response trials; targeted mechanistic studies; and farm-scale techno-economic and ecological validation. Current evidence supports R. ulmifolius as a candidate for structured evaluation, not as a proven practical feed. Any future use should be local, traceable, fruit-free or seed-inactivated, and contingent on maintained intake, digestibility, welfare and performance.