AbstractBatches of wheat silage stored under farm conditions in bunker silos at two locations in Israel were exposed to air for up to 3 days in order to study their aerobic stability. Each batch was examined five times at approximately two month intervals during 1983/84 for changes in dry matter, pH, watersoluble carbohydrates, in vitro digestibility, ash, crude protein, ammonianitrogen, glucose, crude fibre, volatile fatty acids, lactic acid, moulds, yeasts and aerobic bacteria. Consistent changes in silage composition after 3 days of aerobic exposure were noticed with an increase in dry matter and in mould counts, and a decrease in acetic acid and in most cases also in lactic acid. Yeasts and bacteria had a tendency to increase during the 3 days of air exposure.Experiments carried out under laboratory conditions with silages kept at 26°C in an atmosphere of 99% RH showed that after 3 days there was only a slight increase in dry matter, a decrease in acetic and lactic acids, watersoluble carbohydrates and ammonia‐nitrogen, and an increase in the total number of micro‐organisms. Only after 7 days did the deterioration process start.