A Diverse Pasture Grazing System Enhances Ewe and Lamb Performance Over a Three‐Year Grazing Study

High‐output pasture‐based ruminant production systems in temperate regions are typically based on perennial ryegrass ( Lolium perenne L.; PRG) swards. Multispecies swards can improve animal performance; however, evidence from multi‐year, full‐system experiments remain limited. In this context, full‐systems studies are those in which all forage inputs, both grazed and conserved, are produced within the system, enabling integrated evaluation of whole‐farm animal performance over time. This study compared ewe and lamb performance over three production cycles in two grazing systems: (1) Grass‐only (GO) used for grazing and winter feed conservation, and (2) an alternative forage (AF) system comprised of a five‐species multispecies sward: PRG, red clover ( Trifolium pratense L.), white clover ( Trifolium repens L.), chicory ( Cichorium intybus L.) and ribwort plantain ( Plantago lanceolata L.) for grazing, coupled with a PRG plus red clover sward, predominantly used to supply conserved winter feed for ewes on the AF system. Sixty ewes and their lambs were allocated to each system. Animal body weight (BW) and ewe body condition score (BCS) were measured at key production stages. Ewes on the AF system had higher BW ( p < 0.05) and BCS ( p < 0.01) across key production stages. Lambs reared on AF system had higher live weights ( p < 0.01), lifetime average daily gains (238 vs. 179 g day −1 ; p < 0.01) and reached target slaughter weight 37 days earlier ( p < 0.01). These findings demonstrate that alternative forages can enhance ewe and lamb performance while improving efficiency in pasture‐based lamb systems.