Forage accumulation (FA) is a key response in grazing experiments, and estimates of FA in continuously stocked pastures are often obtained using exclosure cages. This study evaluated how 14‐, 21‐, and 28‐d exclusion periods using cages affected morphological, physiological, and morphogenetic responses of continuously stocked ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) pastures maintained at 20‐ and 30‐cm canopy height and how this affected estimates of FA. Grazing exclusion resulted in greater rates of leaf elongation (LER; 1.62 vs. 1.37 cm tiller⁻¹ d⁻¹), stem elongation (SER; 0.16 vs. 0.07 cm tiller⁻¹ d⁻¹), leaf growth (101 vs. 86 kg dry matter [DM] ha⁻¹ d⁻¹), and stem growth (3.4 vs. 1.8 kg DM ha⁻¹ d⁻¹) inside the cages compared with outside. Greater LER resulted in greater final leaf length and leaf area index (LAI) in longer exclusion periods. With greater LAI, photosynthesis was greater within the exclosure cages than on pasture (54.5 vs. 43.9 μmol CO₂ m⁻² s⁻¹). Greater leaf growth rate, together with same tiller population density and leaf senescence rate (LSR) across exclusion periods, resulted in overestimated FA by 14, 26, and 24% for 14‐, 21‐, and 28‐d exclusions, respectively. There was no effect of canopy height on FA, because greater LER and SER values in 30‐cm canopies were compensated by greater LSR. Choice of sites for cage placement by visual appraisal and reduced number of sampling sites resulted on “negative” values of calculated FA for the 14‐d exclusion, making the choice of sampling sites a major source of error in estimation of actual FA. Increasing the number of sampling sites and using indirect measurements of forage mass (FM) may increase the accuracy of FM and FA estimates.

中文翻译：

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重新探讨了开笼技术：连续放牧下的牧场响应及其与放牧实验中草料积累的估计之间的关系

牧草积累（FA）是放牧实验中的关键响应，连续放牧的牧草中FA的估算通常是使用避震笼来获得的。本研究评估使用笼14-，21-和28-d排斥周期如何影响形态学，生理学，不断放养“Mulato II”混合brachiariagrass的形态发生反应（臂形属同义词尾稃草属spp。）的牧场保持在20-和30厘米的树冠高度，以及这如何影响FA的估算。放牧排除导致叶片伸长率（LER; 1.62 vs. 1.37 cm分er ^-1 d ^-1），茎伸长率（SER; 0.16 vs.0.07 cm分− ^-1 d ^-1），叶片生长（101 vs. 86千克干物质[DM]公顷^-1 d ^-1），笼内和外部相比，茎长（3.4 vs. 1.8 kg DM ha ^-1 d ^-1）。较大的LER导致在更长的排除期中更大的最终叶片长度和叶片面积指数（LAI）。LAI越大，排泄笼中的光合作用就比牧场高（54.5 vs. 43.9μmolCO ₂ m ^-2 s ^-1）。在排除期，较高的叶片生长率以及相同的分till种群密度和叶片衰老率（LSR），分别导致14、21和28d排除区的FA分别高估了14％，26％和24％。冠层高度对FA没有影响，因为30cm冠层中更大的LER和SER值可以通过更大的LSR来补偿。通过目测评估选择笼子放置的地点，并减少采样地点的数量，导致14 d排除的计算FA的“负”值，这使得选择采样地点成为估算实际FA的主要误差来源。增加采样点的数量并使用草料质量（FM）的间接测量值可能会提高FM和FA估算的准确性。