Analysis of the nutritive value of timothy grown with varying N nutrition
Analysis of the nutritive value of timothy grown with varying N nutrition
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DOI：
10.1046/j.1365-2494.1998.5320109.x
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发表时间：
1998-06-01
影响因子：
2.4
通讯作者：
McQueen, RE
中科院分区：
文献类型：
--
作者：
Belanger, G;McQueen, RE
施氮对梯牧草生长和产量的影响，但关于它对营养价值的影响有相互矛盾的报道。通过2个试验，研究了4种氮肥水平下不同生育周期（春、夏）田间生长的梯牧草营养价值的变化，并分析了营养价值参数与叶重比（LWR）之间的关系。在再生周期的早期，当可收获的枝条生物量约为200 g干物质（DM）m（-2）时，在非限制性氮和水分条件下，DM的体外真消化率（IVTD）在春季大于夏季，因为中性洗涤纤维（NDF）的浓度较低，其体外细胞壁消化率（IVCWD）较高。但IVTD和IVCWD的下降率和NDF的上升率春季大于夏季。氮缺乏降低IVTD和IVCWD，并增加NDF浓度在再生周期的早期。然而，氮缺乏降低了三个营养价值参数的变化率。到生长周期结束时，IVTD分别为59和42克kg（-1）DM时，不施氮比非限制氮条件下，在春季和夏季。当不施氮时，春季和夏季的IVCWD分别比非限制氮条件下高76和52 g kg（-1）NDF，而NDF浓度分别比非限制氮条件下低35和42 g kg（-1）DM。缺氮增加了叶片在生物量中所占的比例，这在很大程度上可以解释缺氮对梯牧草营养价值的影响。这种积极的影响，氮缺乏营养价值通过生物量中的叶的比例，但是，减少了氮缺乏的负面影响，叶或茎或两者的营养价值。
Nitrogen fertilization affects growth and yield of timothy (Phleum pratense L.), but there are conflicting reports on its effect on nutritive value. Two experiments were conducted to describe changes in nutritive value of field-grown timothy fertilized with four rates of N fertilizer during spring and summer growth cycles, and to analyse relationships between parameters of nutritive value and the leaf to weight ratio (LWR). Early in the regrowth cycles when the harvestable shoot biomass was approximately 200 g dry matter (DM) m(-2) and under non-limiting N and water conditions, the in vitro true digestibility (IVTD) of DM was greater in spring than in summer because the concentration of neutral-detergent fibre (NDF) was lower and its in vitro cell wall digestibility (IVCWD) was greater. However, the rates of decline in IVTD and IVCWD and the rate of increase in NDF were greater in spring than in summer. Nitrogen deficiency decreased IVTD and IVCWD, and increased NDF concentration early in the regrowth cycles. Nitrogen deficiency, however, reduced the rate of change in the three parameters of nutritive value. By the end of growth cycles, IVTD was 59 and 42 g kg(-1) DM greater when no N was applied than with non-limiting N conditions in spring and summer respectively. When no N was applied, the IVCWD was 76 and 52 g kg(-1) NDF greater, whereas the NDF concentration was 35 and 42 g kg(-1) DM less than under non-limiting N conditions in spring and summer respectively. The N deficiency increased the proportion of leaves in the biomass, which can explain for the most part the positive effect of the N deficiency on the nutritive value of timothy. This positive effect of the N deficiency on nutritive value through the proportion of leaves in the biomass, however, was reduced by the negative effect of N deficiency on the nutritive value of leaves or stems or both.