Sorghum panicle residue (SPR), a by-product of Sorghum vulgare, obtained in the manufacture of brooms and wisks, has potential as a partial substitute for grain in growing-finishing diets for feedlot lambs. Accordingly, 48 Pelibuey×Katahdin lambs (initial weight=16.2±4.3 kg) were used in an 84-d growth-performance trial to evaluate its comparative feeding value. Lambs were blocked by weight and assigned within weight groupings to 12 pens (4 lambs per pen). The SPR was finely ground before it was incorporated into the diet. The basal diet contained 60% whole grain sorghum (WGS; DM basis). Dietary treatments consisted in the replacement of WGS with 0, 50, or 100% SPR. Replacement of WGS with SPR decreased (linear effect, P=0.04) average daily gain (ADG), and tended to increase (linear effect, P=0.06) dry matter intake (DMI). Replacement of WGS with SPR decreased (linear effect, P<0.01) gain efficiency (ADG : DMI), and observed dietary net energy (NE), as well as hot carcass weight, dressing percentage, kidney–pelvic–heart fat, and back fat thickness (linear effect, P⩽.05) Other carcass characteristics and wholesale cuts as a percentage of cold carcass weight were not affected by dietary treatments. It is concluded that SPR is a palatable feed ingredient for inclusion in finishing diets for feedlot lambs. The comparative NE values for SPR are 1.50 and 0.91 Mcal/kg for maintenance and gain, respectively, 75% the NE value of WGS. These NE values reflect the greater fiber content of SPR. To the extent that dietary energy density limits energy intake (and hence daily weight gain), appropriate constraints on level of SPR incorporation is warranted.