Submitted to: Journal of Dairy Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/2/2007
Publication Date: 11/1/2007
Citation: Filya, I., Muck, R.E., Contreras-Govea, F.B. 2007. Inoculant effects on alfalfa silage: fermentation products and nutritive value. Journal of Dairy Science. 90(11):5108-5114. Interpretive Summary: The application of lactic acid bacteria to crops when stored in silos is a common practice in the U.S. These bacteria help guarantee the crop (and the resulting silage) will be preserved well in the silo, but they also can have a positive effect on the cow that we do not understand. We performed two trials where we stored (ensiled) alfalfa in laboratory silos with a wide range of commercial lactic acid bacteria (8 commercial products and 6 individual bacterial strains). This report details how these products affected the preservation of the alfalfa silage in the silo, and two subsequent reports will look at how these silages might be digested in the stomach of the cow. In the first trial, all of the products substantially improved preservation in the silo compared with not using a bacterial product. In the second trial, the natural population of lactic acid bacteria on the alfalfa was very high, and only the products that are currently being marketed to farmers improved the preservation of the alfalfa. These results showed that the commercial products tested did improve silage preservation even under difficult circumstances. These results confirm those of other studies that lactic acid bacterial additives can improve alfalfa silage preservation.
Technical Abstract: The effect of fourteen microbial inoculants on the fermentation and nutritive value of alfalfa silages was studied under laboratory conditions. First (477 g dry matter (DM)/kg) and second cuttings (393 g DM /kg) of a second year alfalfa stand were ensiled in two experiments. In both experiments, alfalfa was harvested with standard field equipment. All inoculants were applied at 10^6 colony-forming units (cfu)/g crop. Uninoculated silages served as controls. After treatment, the chopped forages were ensiled in 1.0 and 0.5-L anaerobic glass jars, respectively, at a density of 500 g/L. Each experiment had fifteen treatments (uninoculated control and fourteen inoculants), four silos per treatment. Silos were stored for a minimum of 30 days at room temperature (~22 C). In first cut, all inoculants but one reduced pH relative to the uninoculated control, and all but two of the homofermentative strains shifted fermentation toward lactic acid. In second cut, the epiphytic lactic acid bacteria population was 2.7 x 10^7 cfu/g, and only commercial inoculants produced significant shifts in fermentation. In spite of the positive effects on silage fermentation, 48-h in vitro true digestibility was not improved by inoculation with lactic acid bacteria.