Field indicators of forage nutritive value could help farmers with rapid management decisions to optimize timing and intensity of grazing and meet objectives regarding animal nutrition. The objective of this research was to evaluate the likely relationships among leaf blade nutritive value, herbage mass and leaf stage of pasture regrowth under different growing seasons and residual sward heights. Experiments were performed on perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) pastures during spring and summer of 2016. In both pastures, three residual sward height treatments (3, 6 and 12 cm) were imposed on plots arranged in a split plot design, replicated in three blocks. Sward plots were harvested 5–6 times at intervals spaced 7–10 days apart to measure herbage mass, plant morphology, neutral detergent fibre (NDF), and the 24‐hr in vitro digestibility of NDF (NDFD) and dry matter (DMD) of leaf blades. Pastures showed strong (R²: .62 to .70), but variable, negative relationships between NDFD and herbage mass that varied with the rate at which pasture grew in each season of experimentation. Although there was a consistent NDFD decline as leaf stage of regrowth progressed (R²: .75 to .97), the NDFD also decreased as residual sward height increased, most notably in tall fescue. Additionally, findings indicate that the greater leaf length plasticity of tall fescue compared to residual sward heights may offer opportunities to manage both post‐ and pre‐grazing targets to achieve tall fescue forages with a similar high nutritive value as perennial ryegrass. However, the evaluation of this hypothesis at the farm level and its impacts on animal intake and performance warrants further careful investigations.

中文翻译：

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不同生长和管理条件下多年生黑麦草和高羊茅草的叶片营养价值的田间指标

牧草营养价值的现场指标可以帮助农民做出快速的管理决策，以优化放牧的时机和强度，并达到有关动物营养的目标。这项研究的目的是评估在不同生长季节和残留草皮高度下，叶片营养价值，牧草质量和草场再生长叶期之间的可能关系。对多年生黑麦草（Lolium perenne L.）和高羊茅（Festuca arundinacea）进行实验Schreb。）牧场在2016年春季和夏季。在这两种牧场中，对以分割地块设计布置的地块实施了三个剩余的草皮高度处理（3、6和12 cm），并重复了三个块。间隔5至6天以7至10天的间隔收获草皮图，以测量草料质量，植物形态，中性洗涤剂纤维（NDF）以及NDF（NDFD）和干物质（DMD）在24小时的体外消化率的叶片。牧场表现出很强的（R ²：.62至.70），但是NDFD与牧草质量之间的可变负相关关系随每个实验季节牧场的生长速度而变化。尽管随着再生叶阶段的进行，NDFD持续下降（R ²：.75到.97），NDFD也会随着剩余草皮高度的增加而降低，最明显的是羊茅高。此外，研究结果表明，高羊茅叶片的叶长可塑性要高于残余草皮高度，这可能为管理高放羊茅草饲草后目标和放牧前目标提供了机会，从而获得了与多年生黑麦草相似的高营养价值的高羊茅草饲料。但是，在农场一级对​​该假设的评估及其对动物采食量和生产性能的影响值得进一步仔细研究。