THE GENERAL PATTERN IN SILAGE FERMENTATION IN TWO SUBTROPICAL GRASSES

Three sets of previously‐published experiments have been re‐analysed by numerical methods intended for the elucidation of pattern in sequential data. The results suggest that for Setaria sphacelata cv. Nandi and Chloris gayana cv. Samford Rhodes the stable terminal silage to be expected under subtropical conditions is not the high lactic‐acid silage of temperate regions, but a silage with a relatively high proportion of acetic acid. Lactic‐acid silage is formed, but usually behaves as though in a transitional phase. However, silage made from mature Setaria can be maintained in the lactic‐acid phase by the addition of high percentages of sugar. The silage fermentation can sometimes be retarded, or deflected into an undesirable path for reasons that are not understood. The above patterns suggest three hypotheses for more fundamental investigation. First, since acetic‐acid silage can be expected under most subtropical conditions, its properties require careful investigation. Secondly, relatively young Setaria may be regarded as a source of acetic‐acid silage, but the optimum amount of sugar to be added for ensiling more mature grass needs investigation. Thirdly there is an urgent need to investigate the causes of retardation of fermentation, and of its deflection into an undesirable path, because until these causes are understood, the outcome of ensilage will remain uncertain.