Effect of sodium lignosulfonate and propionic acid application rate on dry matter losses, nutritional composition, in vitro gas production, and fungal populations of high moisture alfalfa hay mini bales

This study evaluated the effects of application rate (AR) of sodium lignosulfonate (MBL) and propionic acid (PRP) on high moisture alfalfa hay spoilage during storage and its nutritive value. Treatments (TRT; MBL and PRP) were applied at four AR: 0 (CON), 2.5, 5 and 10 g/kg (fresh basis) to alfalfa hay at 68.5 % dry matter (DM), packed into mini bales and stored for 33 d. Data were analyzed as a randomized complete block design (5 blocks) with a 2 TRT × 4 AR factorial arrangement. At d 33, DM losses were decreased by PRP at 5 and 10 g/kg ($\overline{x}=$0.9), vs. CON (6.92) and MBL (6.63 ± 1.13 %). Visual moldiness (0–10 ranking) and mold counts were also decreased by PRP at 5 (2.4 and 5.30) and 10 g/kg (0 and 2.7) relative to CON (6.0 and 7.13) and MBL (5.85 ± 0.67 and 7.21 ± 0.31 log cfu/fresh g, respectively). Both TRT kept aNDF and ADF concentrations low at 2.5 g/kg AR (464 and 319) and to a greater extent at 10 g/kg (442 and 307), relative to CON (494 ± 8.1 and 333 ± 4.71 g/kg DM, respectively; P<0.001). Both TRT increased apparent in vitro DM digestibility at all AR relative to CON ($\overline{x}=$543 vs. 501 ± 12.0 g/kg of DM, respectively), but, compared to MBL, PRP also increased the asymptotic maximal gas produced (188.4 vs. 179.7 ± 4.82 mL/g of incubated DM), the rate of gas production (9.46 vs. 8.72 ± 0.45 %/h), and total volatile fatty acids (117.5 vs. 114.8 mM, respectively; P<0.035), due to its greater concentration of nutrients. In conclusion, MBL failed to prevent spoilage of high moisture alfalfa hay while PRP was effective at doses >5 g/kg. However, MBL prevented the increase of aNDF and improved in vitro DM digestibility to the same extent as PRP, possibly due to its strong surfactant properties.