AbstractAn experiment was carried out to study the chemical and bacteriological changes during the ensilage of fresh and partially wilted grass at two different temperature levels. In grass of low dry‐matter content (15.2%) the effect of increasing the temperature to 42° resulted in a clostridial type fermentation, whereas in similar material kept at 20° a lactic acid fermentation occurred. Differences between the two wilted silages were less marked, although the wilted material at low temperature contained more lactic acid than the high‐temperature silage. Results of digestibility trials with sheep did not show any marked variation between treatments, although the digestible crude protein contents were highest in the wet silages. The importance of maintaining low temperatures and of wilting crops prior to ensiling are discussed.