The content of photosynthetic pigments in herbage not only has a strong antioxidant function, but also can improve the health of animals and the quality of livestock products after being ingested by ruminants. Increasing the content of photosynthetic pigments can improve the feed value of herbage, which is of great significance in the process of animal feeding. The experiment aimed to investigate the effect of nitrogen (N) fertilizer levels on the contents of photosynthetic pigments and phytol in fresh Italian ryegrass (IR) herbages and their changes after drying under natural condition over two consecutive seasons. IR variety: Ace (for 2013–2014 season) and Inazuma (for 2015–2016 season) were planted in 3 blocks (4 × 6 m) from two separate fields (≥1 ha), three plots (2 × 2 m) were arranged in each block and three fertilization treatments, control: 0 kg N/ha, 60 N: 60 kg N/ha, and 120 N: 120 kg N/ha, were applied for each block. The results revealed that the crude protein, ether extract, photosynthetic pigments and phytol in IR (fresh herbage and hay) were increased with increasing N fertilizer levels. Photosynthetic pigments decreased obviously by hay preparation (chlorophylls: 40%–70%, phytol: 25%–47%, β-carotene: 72%–90%, lutein: 31%–69%). The decomposition of phytol and β-carotene was not affected by the growing year and N fertilizer levels. However, the decomposition of chlorophyll and lutein was affected by growing year, which was higher in 2014 than that in 2016. Also, the contents of total phytol and lutein of the fresh herbage and hay harvested in 2016 were higher (p < .05) than those harvested in 2014. In conclusion, higher N fertilizer levels could increase the photosynthetic pigments and phytol content in IR fresh herbage which contributes to improving the feed value. However, the content of photosynthetic pigments and phytol in IR hay decreased significantly. IR variety may also affect the nutrient content and their degree of decomposition during drying.

中文翻译：

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不同氮肥水平下意大利黑麦草新鲜牧草和干草光合色素和植醇含量的变化

牧草中光合色素的含量不仅具有很强的抗氧化作用，而且被反刍动物摄食后，还能改善动物的健康和畜产品的品质。提高光合色素的含量可以提高牧草的饲料价值，这在动物饲养过程中具有重要意义。本试验旨在研究氮肥水平对新鲜意大利黑麦草（IR）草本植物光合色素和植醇含量的影响，以及连续两个季节在自然条件下干燥后的变化。IR 品种：Ace（2013-2014 季节）和 Inazuma（2015-2016 季节）从两个不同的田地（≥1 ha）种植在 3 个区块（4 × 6 m）中，三个地块（2 × 2 m）种植在安排在每个区块和三个施肥处理，对照：每块施用 0 kg N/ha、60 N：60 kg N/ha 和 120 N：120 kg N/ha。结果表明，IR（新鲜牧草和干草）中的粗蛋白、醚提取物、光合色素和植醇随着氮肥水平的增加而增加。干草制备后光合色素明显减少（叶绿素：40%–70%，植醇：25%–47%，β-胡萝卜素：72%–90%，叶黄素：31%–69%）。植物醇和β-胡萝卜素的分解不受生长年份和氮肥水平的影响。但叶绿素和叶黄素的分解受生长年份的影响，2014年高于2016年。此外，2016年收获的新鲜牧草和干草的总叶黄素和总叶黄素含量较高( p  < .05)与 2014 年收获的相比。总之，较高的氮肥水平可以增加 IR 新鲜牧草中的光合色素和植醇含量，这有助于提高饲料价值。然而，红外干草中的光合色素和植醇含量显着下降。IR 品种也可能影响干燥过程中的营养成分及其分解程度。