|Reid r l,|
|Puoli j r,|
|Jung g a,|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/11/1994
Publication Date: N/A
Citation: Interpretive Summary: Extension of the grazing season for meat or milk production by ruminants involves producing and utilizing high-quality forages in fall and winter. A variety of Brassica species is used for this purpose in many regions of the world, but not to any extent in the United States, with the exception of the Pacific Northwest. Four years of grazing trials were conducted in West Virginia to evaluate the potential of several Brassicas (kale, hybrid turnip, Chinese cabbage hybrid) for sheep production (fattening lambs, breeding ewes) in the period October to December. Sod seeding in late July gave high yields of dry matter at 90 days, with good chemical composition. Grazing trials (strip grazing) in the first two years gave generally low gains but high carrying capacity of lambs and ewes, and better performance than on stockpiled N-fertilized tall fescue. In the second year, gains on Brassicas were improved by dosing with iodine and copper needles. In the third and fourth years, grazing trials compared lambs performance on hybrid turnip with a Chinese cabbage hybrid (Tyfon) and stockpiled orchardgrass-clover. Supplementary hay was provided in the third year and tested as a variable in the fourth. Lamb gains on Brassicas in both years were high (200 to 330 g/day). Hay improved gains in the first 3 weeks of Brassica grazing, but depressed it thereafter. Thyroid weights in lambs on Brassicas were increased in all years but were not related to weight changes and there was no response in gain to iodine or copper supplementation in later trials.
Technical Abstract: Four years of grazing trials were conducted with Brassica forages to evaluate their quality and effect on ADG of fattening lambs and breeding ewes in late fall. Brassicas tested included kales (Brassica cleracea L. var. acephala DC), turnips (B. rapa L.) and a Chinese cabbage hybrid [B. rapa L. x B. perkinensis (Lour.) Rupr.]. Gains of lambs varied widely between years (from mean ADG of 19 to 330 g/d); ADG on Brassicas were, however, generally higher than on stockpiled tall fescue (Festuca arundinacea Schreb.) or orchardgrass (Dactylis glomerata L.)--red clover (Trifolium pratense L.) pastures grazed at the same time. In 1 yr, dietary supplementation of lambs grazing a hybrid turnip (Forage Star) with iodine and copper oxide needles improved (P<0.5) ADG; however, there was no effect on gains in 2 later yr. In 2 yr, lambs showed higher ADG on Tyfon Chinese cabbage hybrid (241 and 330 g/d) than on Forage Star turnip (195 and 242 g/d) or stockpiled grass-clover (135 and 233 g/d), but yield and grazing days on Tyfon were lower. Indications that supplementary hay improved ADG of lambs and ewes were not confirmed in the final yr, in which hay increased (P<0.5) ADG of lambs in the first 3 wk of grazing Brassicas but decreased gains later. Thyroid weights were increased (P<.01) consistently in all trials on Brassicas, but enlargement was mild and did not relate to ADG. There were no breeding problems in ewes grazing Brassicas. Brassica forages provided high yields (5.6 to 10.5 Mg/ha) of DM in the late fall to early winter period, with high carrying capacity for sheep but unexplained variability in ADG.