Potential of trap-crop radish for fall lamb grazing

After small grains are harvested as hay, grain, or silage in many irrigated areas it is possible to produce a second crop. Brassica species and radish (Raphanus sativus L.) establish quickly and produce high-quality fall and winter forage. Recently, nematode-resistant radish cultivars (trap crops) h ave become available and studies show that they are an effective alternativ e to nematicides for control of the sugarbeet nematode (SBN, Heterodera sch achtii Schmidt). A 2-yr study was conducted to determine the potential of a llowing lambs (Ovis aries) to graze nematode-resistant radish. At Powell, W Y, 'Adagio' trap-crop radish and 'Purple top' forage turnip (Brassica rapa L.) were grown in a replicated and randomized complete block design. Studie s lasted 10 wk in 1994 and 12 wk in 1995. Lambs either grazed radish or tur nip (a host of the SBN) continuously or they grazed radish and turnip, then were transferred to a feedlot diet. Additional groups of lambs received th e feedlot diet for the entire study period. At Manderson, WY, 50 lambs were assigned to each replicate of radish for a 20-d period in 1994. SBN-resist ant radish was comparable to SBN-susceptible turnip in forage production, q uality, and acceptability and weight gain by fall-grazing lambs. Lambs graz ing radish and turnip, without concentrate, produced acceptable market size and carcass grade; but they required longer than feedlot lambs to reach si milar weight. Grazing of trap-crop radish shows promise for recovering expe nses of growing the crop, providing further incentive for including this cr op in sugarbeet (Beta vulgaris L.) rotations.