Limited information is available on the grazing management principles of forage rape (Brassica napus L.), particularly in relation to grazing height and intensity and the impact of these on dry‐matter (DM) yield and nutritive value. A glasshouse study was undertaken to investigate the effect of three defoliation heights (plant height at harvest; DH: 40, 70 and 90 cm; L, M and H DH respectively) and three defoliation intensities (height at which plants were cut; DI: 5, 20 and 35 cm of residual height; H, M and L DI respectively) on forage rape (cv Goliath) yield and nutritive value at two harvests (harvest 1, H1 and harvest 2, H2), and the impact of nitrogen (N) and water soluble carbohydrate (WSC) reserves on regrowth. Increasing DH from L to H increased estimated total DM yield (H1 plus H2) from 0.5 to 4.6 t DM/ha but DI did not affect yield. Dry‐matter yield was optimized at 90 cm DH, but greater nutritive value was achieved by harvesting at lower levels of DH. Despite high in vitro DM digestibility (IVDMD; 852–889 g/kg), harvesting at 90 cm DH could not meet the protein requirement of lactating dairy cows and harvesting at lower levels risks nitrate poisoning. Our results indicate the optimum DH may be between 70 and 90 cm DH, and 20 and 35 cm DI, which requires further studies.

中文翻译：

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饲用油菜的管理策略（甘蓝型油菜）：对干物质产量，植物储量，形态和营养价值的影响

关于牧草强奸（甘蓝型油菜）放牧管理原则的信息有限L.），尤其是放牧高度和强度及其对干物质（DM）产量和营养价值的影响。进行了温室研究，以研究三种脱叶高度（收获时的植物高度； DH：40、70和90 cm； L，M和H DH）和三种脱叶强度（切割植物的高度； DI：两次收获（收获1，H1和收获2，H2）的饲用油菜（cv Goliath）的残留高度分别为5、20和35 cm的剩余高度；分别为H，M和L DI）和营养价值，以及氮素的影响（ N）和水溶性碳水化合物（WSC）可以再生。将DH从L增加到H将估计的DM总产量（H1和H2）从0.5 t DM / ha增加到4.6 t DM / ha，但是DI不会影响产量。在90 cm DH下优化了干物质产量，但是通过在较低水平的DH下收获可获得更大的营养价值。尽管体外DM的消化率很高（IVDMD； 852–889 g / kg），但在90 cm DH处收获不能满足泌乳奶牛的蛋白质需求，而较低水平的收获有硝酸盐中毒的风险。我们的结果表明最佳DH可能在70至90 cm DH之间，而DI在20至35 cm DI之间，这需要进一步研究。