Avaliação de bactérias do ácido lático sobre a conservação de silagens de grãos de milho reidratado

Abstract

The maize hybrids grown in Brazil have a predominantly vitreous endosperm and therefore have low ruminal starch degradation. Among other processes to solve this problem, ensiling ground and rehydrated corn kernels is an easily accessible option for producers. The use of inoculants in this silage is a practice that can optimize fermentation and improve the aerobic stability of the stored material. The aim of this study was to evaluate the use of different inoculants in rehydrated maize grain silage (RMS). Two commercial inoculants of mixed composition, S1 and S2, the Lentilactobacillus hilgardii (LH) strain, the L. farraginis (LF) strain and the combination of S1+LF, were evaluated. The maize was ground (3 mm), rehydrated to 65% dry matter (DM) and inoculated (108 log CFU/kg). The ground maize was rehydrated and compacted manually (density of 1042 ± 11 kg/m3) in 5L experimental silos. The silos were sealed, weighed and stored for 35 and 98 days. The experiment was conducted in a DBC with 5 treatments (LF, LH, S1, S2 and S1+LF) plus 1 control (no inoculant) with 4 replications (blocks on different days of silo production), totaling 48 experimental units. The data was submitted to analysis of variance (SISVAR®). The means were compared using the Scott Knott test at a 5% probability level. There was an effect of the inoculants on DM, starch, BAL, BAFE and yeast populations, fermentation products and aerobic stability. The lowest pH values were observed in silages inoculated with S1 and S2 (average: 3.87). The lowest starch concentrations were observed in S1, S2 and LF+S1 silages. The most efficient inoculants in reducing the yeast population were LF and LH (< 2.00 log CFU/g). Silages inoculated with LF, LH and LF+S1 showed greater aerobic stability after 35 days of storage. The concentrations of 1,2-propanediol and propionic acid increased with storage time and were higher in silages inoculated with LH and LF. The effect of the inoculants on pH, DM loss, lactic acid bacteria population and acetic acid concentration depended on the storage period. At 35 days of storage there was no difference in DM loss, but at 98 days DM loss was lower in silages inoculated with S1 and S2 (0.81% on average for the group). Inoculation with S1 and S2 reduced DM losses, the concentration of butyric acid and pH and increased the concentration of lactic acid without changing the yeast population. However, the addition of these inoculants reduced the aerobic stability of the silages after 98 days of storage. The combination of S1 with L. farraginis increased the aerobic stability of the silages after 35 days of storage. The combination of lactic acid bacteria inoculants in these silages was capable of altering the fermentation process, lowering the pH, inhibiting undesirable microorganisms and promoting more efficient fermentation.