The effect of delayed ensiling and application of a propionic acid-based additive on the fermentation of barley silage.

Prolonged exposure to air can adversely affect the silage fermentation process. To investigate a possible method to overcome this problem, we determined if a buffered propionic acid-based additive, applied to chopped, whole-plant barley exposed to air before ensiling, would affect the subsequent fermentation. Wilted forage was chopped and treated with nothing, or with 0.1% (wt/wt wet forage) of a buffered propionic acid-based additive and ensiled immediately in quadruplicate 20-L laboratory silos. Portions of the chopped forage, untreated and treated, were left in loose piles in a barn for 24 h before ensiling. Another portion of the untreated silage exposed to air for 24 h was also treated with 0.1% of the additive just before ensiling. Prolonged exposure to air before ensiling increased the numbers of yeasts on forages by more than 1,000-fold. The concentrations of water-soluble carbohydrates decreased by more than 50%; the ammonia-N concentrations increased 40%, and pH increased by more than 1 unit as a result of exposure to air. These changes were less in forage that was treated with the additive at chopping. After 60 d, silages of forages that were exposed to air before ensiling had a higher pH, higher concentrations of ammonia-N and butyric acid, and lower concentrations of lactic and acetic acids than silages of forage that had been ensiled immediately after harvest. In situ DM digestibility was lowest in untreated silages that had been exposed to air before ensiling. In contrast, treatment with the additive, applied before or after exposure to air, prevented the reduction in in vitro digestion.