A diverse diet increases animal growth performance and carcass yield of grazing lambs.

The current experiments were conducted across two lamb finishing seasons (2019 [experiment 1; ] and 2020 [experiment 2; ]). In both experiments lambs were provided a monotonous () diet (annual ryegrass [ L.] during 2019 and perennial ryegrass [ L.] and white clover [ L.] during 2020) or a diverse () diet composed of spatially separated strips sown to chicory ( L.), plantain ( L.), perennial ryegrass, lucerne ( L.), and dock (). During Exp1, the DIV lambs had a stocking rate () of either 80, 95, 100, or 110 m/lamb/wk, whereas the MON lambs had a 100 m/lamb/wk SR. In Exp2, the SR aimed to allocate the MON lambs with twice the forage allowance (kg DM/lamb/d) as DIV lambs. In Exp1, all lambs provided DIV had a greater ( < 0.01) average daily gain (; + 130%) than MON rams, independent of the SR. Accordingly, DIV had greater ( < 0.05) hot carcass weight (; + 26%) and aged carcass weight (; + 27%) compared with MON, across all SR. The 80 m/lamb/wk SR tended to have a greater ( = 0.10) dressing percentage and had similar ( = 0.29) drip loss percentage to the MON lambs, while the other DIV lamb SR all had greater ( < 0.05; +12%) dressing percentages and lower ( < 0.05) drip loss percentage than MON lambs. In Exp2, DIV lambs had greater ( < 0.01) ADG (+37%), HCW (+15%), and dressing percentage (+6%) compared with MON lambs. This improved animal performance occurred despite being offered 57% less ( = 0.01) dry matter (), 56% less ( < 0.01) digestible DM, and 57% less ( = 0.02) metabolizable energy per lamb per day. Ultimately, these experiments demonstrate that providing growing lambs a functionally diverse diet improves animal growth performance and carcass weight compared with a monotonous diet of annual ryegrass or a mixed sward containing perennial ryegrass with white clover.