Propionic Acid in the Fermentation and Conservation of Whole Plant Corn Silage at Two Packing Densities

The objective of this study was to evaluate the effects of propionic acid on whole-plant maize silage under two packing densities (608 or 428 kg m−3 for the high and low density (HD and LD), respectively) at 365 g kg−1 dry matter (DM), in terms of gas production, DM content, fermentative losses, aerobic stability, pH, and chemical composition. The treatments were as follows: HD—no additive, positive control; high density with propionic acid (HDPA); LD—no additive, negative control, simulating a pile silo condition; and low density with propionic acid (LDPA). Silos were stored for 60 days. Propionic acid and high packing density decreased total gas production (4.9, 5.5, 5.6, and 5.8 L kg−1 DM for HDPA, LDPA, HD, and LD, respectively; p<0.0001). Propionic acid silages presented higher DM than control silages, being 362.5 and 356.5 g kg−1 DM for PA and control, respectively. Consequently, the control silages showed higher DM losses during fermentation than the propionic acid silages (31.1, 26.3, 13.1, and 7.1 g kg−1 initial DM for LD, HD, LDPA, and HDPA, respectively; p=0.0025). Additionally, propionic acid and the packing densities decreased DM losses during 10 days of aerobic exposure (132.4, 123.0, 96.3, and 85.3 g kg−1 silage DM for LD, HD, LDPA, and HDPA, respectively; p<0.0001). Propionic acid silages showed longer aerobic stability compared to control silages (137, 134, 65, and 32 h for LDPA, HDPA, HD, and LD, respectively; p<0.0001). The LD silages showed the highest maximum temperature during aerobic exposure (44, 39, 38.5, and 36°C for LD, HD, LDPA, and HDPA, respectively; p<0.0001). Propionic acid decreases losses during both the fermentation and after opening the silo for both the density levels.