Silage fermentation characteristics of Italian ryegrass (Lolium multiflorum Lam.) harvested at various times on a sunny day.

摘要

Grasses exhibit diurnal variation in chemical composition and epiphytic microorganisms, which may influence the natural fermentation attributes of silage. The objective was to determine the effect of diurnal changes on chemical composition and epiphytic microorganisms and these effects on fermentation quality of unwilted Italian ryegrass (Lolium multiflorum Lam.) silage. Primary growth of Italian ryegrass was harvested in the heading stage at 0800 (AM), 1300 (M) and 1800 h (PM) on three sunny days. Each cutting time was assayed in triplicate in laboratory silos and sampled after 30 d (cutting Day 1) or serial days until 30 d (other cutting days) to analyze the fermentation attributes and microbial counts. Bacterial community was determined by denaturing gradient gel electrophoresis (DGGE) on pre- and post-ensiled forage samples, which were harvested on cutting Day 2. The results showed that fermentation instability for the silage made with M-cut forage, which had fewer lactic acid bacteria (LAB) species in the early phase of ensiling and where Clostridium sp. was present but no Lactobacillus plantarum at the end of ensiling, resulted in higher (P<0.05) pH value, NH₃-N, and butyric acid for 30-d fermented silages than those made with AM- and PM-cut forages. The concentrations of dry matter (DM) and lactic acid were higher (P<0.05) and the silage pH and NH₃-N were lower (P<0.05) for silage made with PM-cut forage as compared to those made with AM-cut forages. Italian ryegrass cut at 1800 h was associated with good silage fermentation attributes.