Effect of inoculation with Lactobacillus buchneri LB1819 and Lactococcus lactis O224 on fermentation and mycotoxin production in maize silage compacted at different densities

Abstract

We examined the effectiveness of a combined inoculant of hetero-fermentative Lactobacillus buchneri LB1819 and homo-fermentative Lactococcus lactis O224 on quality of maize silage at two different densities. The four treatments were: CTR-LD, untreated at low-density (132 ± 6 kg DM/m3); CTR-HD, untreated at high density (186 ± 6 kg DM/m3); TRT-LD, inoculated at low density; and TRT-HD, inoculated at high density. The 5 replicates for each treatment were ensiled in 20-L plastic jars and the inoculant was applied at a rate of 250,000 CFU/g ensiled forage. The fermentation profile, aerobic stability, and DM losses were measured after 2, 4, 8, 16, and 32 days of ensiling, and the chemical composition, microbial counts, and concentrations of mycotoxins were assessed in the 32 day samples. Data measured once during experiment were analyzed according to a completely randomized design (CRD), with a 2 × 2 factorial arrangement of treatments (i.e., inoculation, density, and their interaction). Data measured at different time points were analyzed according to a CRD, with a 2 × 2 × 5 factorial arrangement of treatments (i.e., inoculation, density, length of ensiling, and their first or second order interactions). The lactic acid concentration increased (P < 0.05) with the duration of ensiling, with no differences among treatments (overall means on day 2 and day 32: 26.7 and 50.9 g/kg DM, respectively). Aerobic stability was greatest (P < 0.05) in the TRT-HD silage at 32 days. After 32 days of ensiling, soluble crude protein was greater in the CTR-HD and TRT-LD silages than the CTR-LD and TRT-HD silages (P < 0.05, inoculation × density interaction). The treatments had similar chemical parameters, yeast and mould counts (overall mean: 4.53 log10 CFU/g and 1.59 log10 CFU/g, respectively). The overall concentration of aflatoxin B1 was 0.412 μg/kg DM. The CTR groups had higher concentrations of fumonisin B2 (413 vs. 278 μg/kg DM, P < 0.05) and roquefortine C (22.81 vs. 3.39 μg/kg DM, P < 0.05) than the TRT groups. Conversely, the CTR groups had lower concentrations of fusaric acid than the TRT groups after 32 days (2849 vs. 4162 μg/kg DM, P < 0.05). Both CTR and Lactobacillus buchneri LB1819 and Lactococcus lactis O224 treated samples at a high silage density increased the aerobic stability after 32 days of ensiling (P < 0.05, day × density interaction). Results indicated that inoculation and use of a greater silage density enhanced the fermentation and aerobic stability of maize silage.