Effects of nitrogen fertilization levels and wilting periods on chemical composition and chlorophyll content of Italian ryegrass harvested at different stages

摘要

Meat and milk produced by ruminants contain some trace compounds derived from plant chlorophyll (Chl), such as 1-phytene and phytanic acid, which affect sensory property and bioactivity of these products.However, factors affecting the content of Chl related compounds in preserved forages are unclear.The objective of this study was to investigate the post harvest changes in chemical composition and chlorophyll content of Italian ryegrass (IR) grown under different levels of nitrogen (N) fertilization.The forage grown under the different fertilization (0, 60 and 120 kg N/ha, topdressed in early spring) was harvested at both late vegetative and early bloom stage, and was wilted under natural condition for 1, 2 or 7 days.Chemical composition and Chl contents in whole plant were measured for the raw and wilted IR.For both maturity stages, the contents of crude protein, ether extract, neutral detergent fiber and Chl in raw and wilted IR increased (P ＜ 0.01), while non-fibrous carbohydrate content decreased (P ＜ 0.01) with the increase of N fertilization levels.The Chl content did not change during first 2 day wilting period, but decreased obviously after 7 days (P ＜ 0.01), irrespective of fertilization levels.The Chl contents at late vegetative stage were higher (P ＜ 0.01) than those at early bloom stage.The results indicate that the N fertilization levels and maturity stages affect the Chl content of Italian ryegrass, whereas Chl content are not largely affected by wilting within 2 days.