Microbial approach to improving aerobic stability of silage

Abstract

Aerobic deterioration of silage is a major challenge in the feed value chain. This review discusses microbial mitigations to improving aerobic stability of silages. Early detection of silage deterioration at the face of the silo is important to reduce further ingress of spoilage organisms into deeper layers of the silage. The traditional use of thermocouples to measure spot-temperature in aerobically-exposed silages is laborious. Thermal cameras are now used to instantly visualize heat distribution over the silo face by examining thermographs generated in real-time. Microbial mitigation of aerobic silage deterioration remains the safest and most reliable strategy of reducing losses during feed-out. Three generations of microbial additives that have been used to improve the aerobic stability of silages include first generation (1 G), second generation (2 G) and third generation (3 G) silage inoculants. Homolactic fermentation by 1 G produces the highest concentration of lactic acid but 1 G are less capable of reducing aerobic spoilage. Second generation and 3 G both have a dual benefit of improving aerobic stability, and ruminal fibre digestion and growth performance. Although heterolactic fermentation by 2 G and 3 G may cause minimal dry matter losses, improvements in fibre hydrolysis during ensiling and reduction in aerobic spoilage may outweigh these losses. Treatment of tropical forages which have higher concentrations of recalcitrant fibres, with 3 G inoculants could have benefits on ruminal fibre digestion. Development of fourth generation inoculants, possessing 3 G properties but capable of thriving intra-ruminally should be the focus of future research on silage inoculants.