Laboratory ensilage of three tropcal pasture legumes - Phaseolus atropurpureus, Desmodium intortum and Lotononis bainesii

Abstract

Phaseolus atropurpureus, Desmodium intortm, and Lotononis bainesii were ensiled in laboratory silos. Molasses was added to the first two legumes at 0, 2, 4, and 8 per cent of their wet weight. Changes in pH and water activity (Aw) and in contents of lactic acid, volatile acids, and volatile bases were followed during storage. When no molasses was added, P. atropurpureus made poorly preserved silage, D. intortum had some of the features of well preserved silage, and L. bainesii made excellent silage. Only 15 per cent of the nitrogen in the D. intortm silage was present as volatile bases, even though the pH remained above 5.0. No explanation was found for this, but the effects of a rapid release of acetic acid during the initial stages of ensilage deserve further study. The preservation of L. bainesii was probably not due solely to the development of acid conditions (pH <.4.2) as the pH at five days was as high as 4.9. P. atropurpureus and D. intortum with 8.0 per cent of molasses made well preserved lactic-acid silage but the smaller additions usually gave rise to butyric-acid silage. Measurements of water activity (Aw) suggested that low values during the initial stages of ensilage were a prerequisite for the production of stable lactic-acid silage.