Nutritive value, silage fermentation characteristics, and aerobic stability of round-baled, alfalfa-grass forages ensiled at 2 moisture concentrations with or without a propionic-acid-based preservative

Objective: Propionic-acid-based products are used commonly for storage of dry hay but are not often consid-ered when ensiling baled forages. The objectives for this study were to test several application rates of a propionic-acid-based preservative on the storage efficiency, nutrient preservation, fermentation characteristics, and aerobic stability of alfalfa-grass silages. Materials and Methods: This study evaluated 4 pre-servative treatments applied to alfalfa-grass forages that had received 5.1 mm of unexpected rainfall during wilting. A propionic-acid-based preservative was applied at rates of 0.01 (control), 0.13, 0.44, or 0.80% of wet bale weight to 24 (1.2 x 1.2 m) round bales made at either 43.6 or 51.6% moisture. Aerobic stability was then evaluated by remov-ing plastic film from all bales and monitoring surface bale temperatures for 11 d during spring. After exposure, sur-face and core samples were evaluated further for residual fermentation products and pH. Results and Discussion: Before fermentation, forage pH declined linearly (P < 0.001) from 6.14 to 5.77 with increasing pro duct-application rates. After 242 d of stor-age, there were linear increases in concentrations of total alcohols (P = 0.002), and particularly 2,3-butanediol (P < 0.001), with increasing preservative application rates. After aerobic exposure, maximum surface temperatures (0.15-m depth) declined linearly (P = 0.001) from 55.6 to 17.9 degrees C with preservative application rate. A similar linear (P = 0.002) effect was observed for exposed surface pH (range = 6.52 to 5.41). Implications and Applications: Propionic-acid-based preservatives improved aerobic stability of round -bale silages, but the additional cost must be a critical component of any overall management strategy.