NEW TRENDS AND OPPORTUNITIES IN THE DEVELOPMENT AND USE OF INOCULANTSFOR SILAGE

Inoculants are used as silage additives to improve preservation effici ency and to enhance animal performance. In most commercially available inoculants, homofermentative lactic acid bacteria (LAB) have been use d because they are fast and efficient producers of lactic acid, improv ing natural silage fermentation. Specific LAB inoculants may also have beneficial effects on animal performance even if there is no effect o n fermentation. However, these types of inoculants are not always adva ntageous. They do not necessarily prevent secondary fermentation by cl ostridia in moist silages, and they sometimes impair the aerobic stabi lity of grass and small grain silages, Therefore, new criteria for sil age inoculants should be established which consider the specific needs of the crop being ensiled. New approaches which are being taken to de velop improved inoculants for silage include the following: (1) using LAB isolates which are more specific to the target crops; (2) inclusio n of heterofermentative LAB to produce volatile fatty acids to inhibit yeasts and moulds upon aerobic exposure; (3) inclusion of organisms o ther than LAB in inoculants to inhibit detrimental microorganisms; (4) selection or engineering of LAB strains to inhibit specific microorga nisms; and (5) cloning and expression of genes which would enable sele cted LAB strains to utilize polysaccharides in crops which are low in soluble carbohydrates. Many of these new strategies for formulating in oculants are being tested, but further research is needed to determine the most successful approaches.