Aerobic stability and in vitro fiber digestibility of microbially inoculated corn and sorghum silages.

Silage deteriorates readily when exposed to air, resulting in DM losses. Inoculation of silage with lactic acid bacteria may aid fermentation, but effects on aerobic stability are unclear. Two experiments were conducted to determine the effect of commercial bacterial inoculants on aerobic stability and in vitro fiber digestibility of silage. Corn (Zea mays L.; Exp. 1) or sorghum (Sorghum bicolor [L.] Moench; Exp. 2) forage (30% DM) was inoculated (1.1 x 10(5) colony forming units/g of fresh forage) with lactic acid bacteria (Pioneer brand 1174 on corn, Pioneer brand 1129 on sorghum) or bacterial inoculant plus an antifungal agent (potassium sorbate at .5 mg/g of fresh forage) and ensiled in 19-L microsilos. Corn was ensiled for 40 or 186 d and sorghum was ensiled for 30 or 160 d (five microsilos per treatment per ensiling time combination). Silages were exposed to air for 7 to 9 d after opening, and temperature was monitored daily. Water-soluble carbohydrates, pH, NDF, ADF, and in vitro digestibility of NDF and ADF were determined before and after ensiling and on exposed silages. Inoculation reduced (P < .05) silage pH in both corn and sorghum but did not prevent aerobic deterioration of the silages. Temperatures during aerobic exposure of silages did not differ (P > .05) between uninoculated and inoculated silages. Inoculant treatment did not affect (P > .05) concentrations or digestibility of NDF in corn; however, NDF and ADF concentration and in vitro digestibility of NDF increased (P < .05) with time of ensiling in sorghum silage, and in vitro ADF digestibility increased (P < .05) with time of ensiling in corn silage.