EVALUATION OF BRASSICAS IN GRAZING SYSTEMS FOR SHEEP .1. QUALITY OF FORAGE AND ANIMAL PERFORMANCE

Four years of grazing trials were conducted with Brassica forages to e valuate their chemical composition and effect on ADG of fattening lamb s and breeding ewes in late fall. Brassicas tested included kales (Bra ssica oleracea L. var. acephala DC), turnips (B. rapa L.), and a chine se cabbage hybrid (B. rapa L. x B. pekinensis [Lour.] Rupr.). Daily ga ins of lambs varied widely among years (19 to 330 g/d); ADG on Brassic as were, however, generally higher than on stockpiled Kentucky 31 tall fescue (Festuca arundinacea Schreb.) or orchardgrass (Dactylis glomer ata L.)-red clover (Trifolium pratense L.) pastures grazed at the same time. In 1 yr, dietary supplementation of lambs grazing a hybrid turn ip (Forage Star) with iodine and copper oxide needles improved (P < .0 5) ADG; however, there was no effect on gains in two later years. In 2 yr, lambs showed higher ADG on Tyfon chinese cabbage hybrid (241 and 330 g/d) than on Forage Star turnip (197 and 275 g/d) or stockpiled gr ass-clover (135 and 233 g/d), but yield of Tyfon was lower. Indication s that supplementary hay improved ADG of lambs and ewes were not confi rmed in the final year, in which hay increased (P < .05) ADG of lambs in the first 3 wk of grazing Brassicas but decreased gains later. Thyr oid weights were increased (P < .01) consistently in all trials on Bra ssicas, but enlargement was modest and not related to ADG. Brassica fo rages provided high yields (5.6 to 10.5 t/ha) of DM in the late fall t o early winter period, with high carrying capacity for sheep but large variability in ADG.