Central Mississippi Research and Extension Center, Mississippi State University, Raymond, USA.
J Dairy Sci. 2011 Aug;94(8):3949-59. doi: 10.3168/jds.2010-3947.
Cool-season annual forages provide high-quality herbage for up to 5 mo in the US Gulf Coast states, but their management in pasture-based dairy systems has received little attention. Objectives of this study were to evaluate pasture and animal responses when lactating Holstein cows (n=32, mean DIM=184±21) grazed either N-fertilized rye (Secale cereale L.)-annual ryegrass (Lolium multiflorum Lam.) mixed pastures or rye-annual ryegrass-crimson clover (Trifolium incarnatum L.)-red clover (Trifolium pratense L.) pastures at 2 stocking rates (5 vs. 2.5 cows/ha) and 2 rates of concentrate supplementation [0.29 or 0.40 kg of supplement (as is)/kg of daily milk production]. Two cows paired by parity (one multiparous and one primiparous) were assigned randomly to each pasture. The 2 × 2 × 2 factorial arrangement of treatments was replicated twice in a completely randomized design. Forage mixture and supplementation rate did not affect milk production during three 28-d periods. Greater milk production occurred at the low (19.7 kg/d) than the high (14.7 kg/d) stocking rate during periods 2 and 3, but production was similar during period 1. Despite lower production per cow, milk production per hectare was generally greater at the high stocking rate (81.6 vs. 49.5 kg/ha). Generally, greater pregraze herbage mass on pastures at the lower stocking rate (1,400 vs. 1,150 kg/ha) accounted for greater herbage allowance. Both forage (8.0 vs. 5.9 kg/d) and total (14.1 vs. 11.6) organic matter intake were greater at the low stocking rate. Cows fed less supplement had greater forage organic matter intake (8.0 vs. 6.1 kg/d). Greater herbage mass was associated with the greater intake and subsequent greater milk production. Differences in forage nutritive value, blood metabolites and milk composition, although showing some response to treatments, may not be of sufficient magnitude to affect choice of pasture species or other management practices. Animal performance was not improved by adding clovers to mixed cool-season grass pastures like those in this study. Stocking rate had a major effect on pasture and animal performance. During the cool season, supplementation with concentrates should be planned based on estimated energy intake from forages to achieve optimum milk production and ensure maintenance of body condition.
冷季一年生牧草在美国墨西哥湾沿岸各州可提供长达 5 个月的高质量草料，但在牧场奶牛系统中的管理却鲜有关注。本研究旨在评估当泌乳荷斯坦奶牛（n=32，平均 DIM=184±21）放牧于氮肥施肥黑麦（Secale cereale L.）-一年生黑麦草（Lolium multiflorum Lam.）混播草地或黑麦-一年生黑麦草-红三叶草（Trifolium incarnatum L.）-白三叶草（Trifolium pratense L.）草地时，牧场和动物的反应，采用 2 种放牧率（5 或 2.5 头/公顷）和 2 种精料补饲率[0.29 或 0.40 kg 补饲（原样）/kg 日产奶量]。按照每胎次（1 头经产牛和 1 头初产牛）配对，将 2 头奶牛随机分配到每个牧草地。采用完全随机设计，将 2×2×2 因子处理设计重复 2 次。在 3 个 28 天的周期中，饲草混合物和补饲率对产奶量没有影响。在第 2 和第 3 周期中，低（19.7 kg/d）而非高（14.7 kg/d）放牧率下的产奶量更高，但在第 1 周期中，产奶量相似。尽管每头牛的产奶量较低，但高放牧率下的每公顷产奶量（81.6 与 49.5 kg/ha）通常更高。一般来说，较低放牧率（1400 与 1150 kg/ha）下的牧场预放牧期牧草生物量更高，从而可提供更多的牧草允许量。低放牧率下的干物质采食量（8.0 与 5.9 kg/d）和总干物质采食量（14.1 与 11.6 kg/d）均更高。补饲较少的奶牛的饲草干物质采食量更高（8.0 与 6.1 kg/d）。更大的牧草生物量与更高的采食量和随后更高的产奶量相关。饲草营养价值、血液代谢物和牛奶成分的差异虽然对处理有一定的反应，但可能没有足够的幅度来影响牧场物种的选择或其他管理实践。在本研究中，向冷季混播草地添加三叶草并没有提高动物的生产性能。放牧率对牧场和动物性能有重大影响。在凉爽季节，应根据饲草的估计能量摄入量来计划精料补饲，以实现最佳产奶量并确保维持体况。
