Changes of fumonisin production in rice grain during ensiling.

We assessed fumonisin production during the ensiling of rice grain. Rice grain was harvested at the full-ripe stage and prepared as rough rice, crushed rough rice, brown rice or crushed brown rice. Each material was ensiled under six conditions: (1) no fungus, anaerobic; (2) no fungus, aerobic; (3) water added, anaerobic; (4) water and fumonisin-producing fungus added, anaerobic; (5) water and fumonisin-producing fungus added, aerobic; or (6) fumonisin-producing fungus added to autoclaved material, aerobic. After 40 days of ensilage, we analyzed the silage fermentative quality and fumonisin concentration. The fermentative quality of all materials was good in treatments (3) and (4) (pH < 4), reasonable in treatment (5) (pH = 5∼6) and unacceptable in treatments (1) and (2) (pH > 6.5). The fumonisin concentration was low in all materials in treatments (1) to (4), slightly increased in the three materials other than rough rice in treatment (5), and enormously increased in all materials in treatment (6). The results indicate that the fumonisin-producing fungus does not produce fumonisin in anaerobic conditions. It is important that an anaerobic condition be maintained during ensiling in order to reduce the fumonisin content in rice grain silage.