Different aspects of Lactobacillus inoculants on the improvement of quality and safety of alfalfa silage

Krystyna Zielińska1, Agata Fabiszewska2*, and Ilona Stefańska1
There is a significant range of bacterial inoculants for forage ensiling, but there is still a need for formulations to improve the safety of feed. The objective of the study was to evaluate the usefulness of three lactobacilli strains in alfalfa (Medicago sativa L.) The following bacterial inoculants were used: Lactocacillus plantarum K KKP 593p (LPK), L. plantarum C KKP 788p (LPC), L. buchneri KKP 907p (LB), and mix of all three strains (LPK+LPC+LB). The application of bacterial inoculants in alfalfa ensiling resulted in a reduction of the total number of molds, Clostridium perfringens and Listeria sp. (up to 5, 7, and 5 times respectively for LB inoculant in comparison to untreated silage). Total inhibition of Salmonella sp. and Escherichia coli growth was achieved in silages treated with all inoculants except for LPC. Aerobic stability in the control silage was the lowest (77 h) and doubled under the influence of bacterial inoculants. The most stable according to aerobic stability was silage treated with LB inoculant (175 h), where the highest concentrations of acetic acid (4.8 g kg-1), propionic acid (0.7 g kg-1) and 1,2-propanediol (526 mg kg-1) were reported. The study discussed that it is important to evaluate not only the effect of bacterial inoculants on physicochemical and microbiological silage properties, as the presence and expression of antibiotic resistance genes in lactic acid bacteria have been reported. The results of antimicrobial susceptibility testing of the strains showed that almost all minimum inhibitory concentrations values for eight antibiotics were equal to or below the corresponding breakpoints proposed by the European Food Safety Authority, Additives and Products or Substances used in Animal Feed Panel.
Keywords: Aerobic stability, alfalfa, antibiotic susceptibility, Lactobacillus, pathogenic bacteria, silage.
1Prof. Wacław Dąbrowski Institute of Agricultural and Food Biotechnology, Department of Fermentation Technology, 36 Rakowiecka St., 02-532 Warsaw, Poland.
2Warsaw University of Life Sciences, Faculty of Food Sciences, 159 c Nowoursynowska St., 02-787, Warsaw, Poland *Corresponding author (agata_fabiszewska@sggw.pl)