Recent Advances in Bacterial Silage Inoculant Technology

The concept of using cultures of lactic acid bacteria to enhance silage fermentation developed near the beginning of the last century but early cultures had insufficient bacteria and little success until freeze drying and encapsulation techniques were developed (Weinberg and Muck, 1996). Traditional silage inoculants were developed to acidify crops during anaerobic storage and thereby minimize losses of dry matter and nutritive value during storage. Such inoculants contained homolactic bacteria to dominate the epiphytic bacteria population, thereby ensuring the fermentation of plant sugars into lactic acid. The lactic acid accumulation reduced pH to levels that inhibited the growth of spoilage organisms, reduced dry matter (DM) losses, preserved the nutritive value of the silage, and in some cases enhanced animal performance. Initially, many inoculants contained only Lactobacillus plantarum because of the vigorous growth, acid tolerance, and high lactic acid production potential of this organism. Later, other faster-acting bacteria (Pediococcus pentosaceus, P. acidilacti, Enterococcus faecium, and L. acidophilus) were included with L. plantarum to ensure that consistent positive results were achieved (Weinberg and Muck, 1996). Additional modifications included direct addition of fermentable substrates to inoculants or inclusion of enzymes to hydrolyze polysaccharides into fermentable sugars. Muck (1993) reviewed trials published between 1985 and 1992 and reported that inoculant application improved fermentation indices (pH, lactic:acetic acid ratio, and ammonia-N) in about 60% of studies. Feed intake and body-weight gain, were increased in about 25% of studies, whereas milk production was increased in 40% of studies. A later review of studies published between 1990 and 1995 reported that inoculation had a similar level of success at improving fermentation indices, but noted that aerobic stability was increased less than a third of the time (Muck and kung, 1997). In fact, the authors noted that inoculant application had no effect on aerobic stability a third of the