Grazing methods and stocking rates for direct-seeded alfalfa pastures: II. Pasture quality and diet selection.
Grazing methods and stocking rates for direct-seeded alfalfa pastures: II. Pasture quality and diet selection.
复制标题
直播苜蓿草场的放牧方式和载畜量：二．
作者：
M. Schlegel;C. Wachenheim;M. E. Benson;N. Ames;S. Rust
通过2年的试验研究了两种放牧方式（GM）和两种载畜率（SR）对紫花苜蓿（Medicago sativa L.）变种WL225）牧草质量和荷斯坦牛日粮选择。1988年播种了8块牧场（0.76公顷），并分成两块，每块4块牧场。牧场管理，允许36天的休息期，平均放牧季节为105天。在公牛进入下一个围场，苜蓿植物的冠层高度（CH）进行了测定和牧草，牧草样品进行了收集。分析了粗饲料样品的DM、OM、CP和体外OM消化率（IVOMD）。在12天的时间间隔开始与第二个放牧周期，extrusa样本收集与食管瘘的阉牛。将逼尿肌样品冷冻、冻干，并分析OM、CP、IVOMD、原位瘤胃DM降解和瘤胃不可降解蛋白。GM对苜蓿CH或牧草DM、OM、CP和IVOMD无影响。增加SR增加牧草CP含量在这两年和增加DM，OM，和IVOMD在第二年。GM或SR对瘘管阉牛选择的牧草品质无影响。食道瘘管牛选择的饲料，有更大的OM，CP和IVOMD比平均营养含量的饲料。虽然饲料质量是更大的放养率增加时，每头动物的饲料数量可能有有限的收益。
A 2-yr study was conducted to determine the effects of two grazing methods (GM) and two stocking rates (SR) on alfalfa (Medicago sativa L. var. WL225) pasture quality and diet selection by Holstein steers. Eight pasture plots (.76 ha) were seeded in 1988 and divided into two blocks of four pastures each. Pastures were managed to allow a 36-d rest period with an average grazing season of 105 d. Before steers entered the next paddock, canopy heights (CH) of alfalfa plants were determined and pasture-forage samples were collected. Forage samples were analyzed for DM, OM, CP, and in vitro OM digestibility (IVOMD). At 12-d intervals beginning with the second grazing cycle, extrusa samples were collected from steers with esophageal fistulas. Extrusa samples were frozen, freeze-dried, and analyzed for OM, CP, IVOMD, in situ ruminal DM degradation, and ruminal undegradable protein. There were no effects of GM on alfalfa CH or pasture DM, OM, CP, and IVOMD. Increasing the SR increased pasture CP content in both years and increased DM, OM, and IVOMD in the 2nd yr. There was no effect of GM or SR on the quality of forage selected by esophageally fistulated steers. Esophageally fistulated steers selected forage that had greater OM, CP, and IVOMD than the average nutrient content of the forage. Although forage quality was greater when stocking rates were increased, the quantity of forage available per animal may have limited gains.