Fermentation is an environmentally friendly method to improve feed quality. Fermented liquid feed and airtight stored moist crimped cereal grain systems that are of increasing importance in agricultural practice were studied. Both rely on spontaneous microbial developments with poorly understood population dynamics, resulting in unpredictable final quality. Temperature, fermentation time and ingredients affected final properties of the feed. Molecular-based species identification showed that microbial populations changed, even when total viable counts were stable. Moisture contents in farm-stored crimped cereal grain were mostly below recommended values, resulting in insufficient lactic acid formation and growth of undesirable microbes. Adding starter cultures to fermentation systems influenced microbial populations. A grass silage lactic acid bacteria starter culture was added to liquid feed fermentations. Lactobacillus plantarum of the starter consortium grew well, but Lactobacillus panis from the feed ingredients dominated both inoculated and non-inoculated fermentations. The starter culture did not influence yeast populations. Starter strains should be adapted to the system and may include appropriate yeasts. The lactic acid bacteria Lactobacillus fermentum, L. panis and Pedicoccus pentosaceus, and the yeasts Pichia fermentum and Pichia anomala may be included in such starter cultures. Adding the biocontrol yeast P. anomala to moist crimped cereal grain decreased numbers of undesirable moulds and reduced Enterobacteriaceae by 5 log units during storage. Feeding animals with P. anomala inoculated grain did not adversely affect performance, but only marginally improved weight gain. The yeast contribution to protein content was insufficient to describe the grain as protein feed. This is possibly due to cell density dependent growth inhibition of the yeast, as maximum P. anomala levels on grain, regardless of treatments, never exceeded 8.5 log units. Inoculation of P. anomala with high phytase activity into crimped cereal grain reduced grain phytate levels. Bound phosphorus, in the form of inositol phosphates, was not detected in any of the liquid diets after fermentation
