BACKGROUND: Lactic acid bacteria inocula have been developed over the years to improve the aerobic stability of silages. The aims of the study were to evaluate the effect of various conservation periods and the use of Lactobacillus hilgardii inoculum on aerobic stability, fermentative profile and microbial population of corn and sorghum silages. Trials were carried out on two corns and one sorghum crops. The crops were untreated or treated with L. buchneri (LB, application rate 300 000 cfu g −1 FM), L. hilgardii (LH, application rate 300 000 cfu g −1 FM) and a combination (LB + LH, application rate 150 000 cfu g −1 FM each). Silos were opened after 15, 30, 100 and 250 days of conservation, and the silages were analysed for fermentative profile, microbial count and aerobic stability. RESULTS: During conservation, the inocula influenced the fermentation profile. The use of LH increased the aerobic stability at 15 and 30 days in one out of three trials, while after 100 and 250 days, the presence of LB alone or with LH led to greater stability. In all the trials, the acetic acid content increased, the yeast count decreased and the aerobic stability increased during the conservation period. CONCLUSIONS: This study has shown that a long period in complete anaerobiosis reduced yeast count and improved aerobic stability in all silages. The addition of LB was confirmed to be a good option for increasing aerobic stability of silages, whereas the effect of LH alone or in combination with LB on aerobic stability was not consistent between trials. Sample preparation and analysesAll replicates of pre-ensiled material and the silage were split into five subsamples. One subsample was analysed immediately for the DM content by oven drying at 80 ∘ C for 24 h. DM was corrected according to Porter and Murray,25 in order to consider the losses of volatile compounds that can take place at 80 ∘ C. The second subsample was oven-dried at 65 ∘ C to constant weight and was air-equilibrated, weighed and ground in a Cyclotec mill (Tecator, Herndon, VA, USA) to pass a 1 mm screen. The dried samples were analysed for total nitrogen, according to the Dumas method (method number 992.23), 26 using a nitrogen analyser (Primacs SN, Skalar, Breda, The Netherlands), for crude protein (CP) (total N × 6.25), for ash by ignition (method number 942.05), 26 for water-soluble carbohydrates (WSC), by the phenol sulfuric acid method, according to DuBois et al., 27 and for ether extract (EE), J Sci Food Agric 2019; 99: 2530-2540

A set of kinetic tests on a promoted Ru/C catalyst for ammonia synthesis has been carried out under industrially relevant reaction conditions (T = 370−460 °C, P = 50−100 bar). The results have been elaborated by using some kinetic models either derived from literature or here-developed. The best results, as for fitting and consistency of the optimized parameters, were obtained by simply modifying the Temkin equation with the addition of H2 and NH3 adsorption terms, to take into account their inhibiting effect on catalyst performance. Such an equation can be advantageously applied for better design and operation of ammonia synthesis reactors using Ru/C catalysts. The activation energy for the synthesis reaction was 23 kcal/mol, much lower than that previously found for Fe-based catalysts. From a practical point of view, it has been shown that the working pressure can be decreased, with the same plant productivity, by 40−50% when using the present Ru/C catalyst. Likewise, the ammonia concentration in the exit gas can be increased by about the same value if the working pressure is not decreased.

The growth of Aspergillus flavus and the production of aflatoxins (AF) during the aerobic deterioration of corn silage represent a problem for animal and human health. This experiment was conducted to evaluate whether the presence of A. flavus and AF production originate from the field or additional AF are produced during the fermentation phase or during aerobic deterioration of corn silage. The trial was carried out in northern Italy on corn at a dry matter (DM) level of 34%. The fresh herbage was either not treated (C) or treated with a Lactobacillus buchneri (LB) NCIMB 40788 [(at 3 × 10 5 cfu/g of fresh matter (FM)], Lactobacillus hilgardii (LH) CNCM I-4785 (at 3 × 10 5 cfu/g of FM), or their combination (LB+LH; at 1.5 × 10 5 cfu/g of FM of each strain) ensiled in 20-L silos and opened after 250 d of ensiling. After silo opening, the aerobic stability was evaluated and samples were taken after 7 and 14 d of air exposure. The pre-ensiled material, the silages at silo opening, and the aerobically exposed silages were analyzed for DM content, fermentative profiles, microbial count, nutritive characteristics, DM losses, and AFB 1 , AFB 2 , AFG 1 , and AFG 2 contents. Furthermore, a subsample of colonies with macromorphological features of Aspergillus section Flavi was selected for AF gene pattern characterization and in vitro AF production. The presence of A. flavus was below the detection limit (<1.00 log 10 cfu/g) in the fresh forage before ensiling, whereas it was found in 1 out of 16 silage samples at silo opening at a level of 1.24 log 10 cfu/g. The AF were found in both the fresh forage and at opening in all the samples, with a predominance of AFB 2 (mean value of 1.71 μg/kg of DM). The inocu-lation of lactic acid bacteria determined a reduction in the lactic-to-acetic ratio compared with the control. A larger amount of acetic acid resulted in a lower yeast count and higher aerobic stability in the treated silages than in the control ones. At the beginning of aerobic deterioration, the yeasts increased to over 5 log 10 cfu/g, whereas the molds were close to the value observed at silo opening. When the inhibiting conditions were depleted (pH and temperature higher than 5 and 35°C, respectively), both the total molds and A. flavus reached higher values than 8.00 and 4.00 log 10 cfu/g, respectively, thus determining the ex novo production of AFB 1 during aerobic deterioration, regardless of treatments. The analysis of gene pattern showed that 64% of the selected colonies of A. flavus showed the presence of all 4 AF gene patterns, and 43% of the selected colonies were able to produce AF in vitro. During air exposure, after 1,000°C·h have been cumulated, starch content decreased (below 10% DM) and concentration of neutral detergent fiber, acid detergent fiber, hemicelluloses, crude protein, and ash increased. The inoculation with LB and LB+LH increased the aerobic stability of the silages and delayed the onset of aerobic microbial degradation, which in turn indirectly reduced the risk of A. flavus outgrowth and A...

The environment temperature and its effect on the temperature of silage is very important for the fermentation and subsequent quality of a silage. Obligate heterofermentative lactic acid bacteria (LAB) inocula, because of their ability to inhibit yeasts, have been developed to prevent the aerobic deterioration of silages. The temperature during silage conservation may also play an important role in the fermentation profile of silages. This study has evaluated the effect of temperature, during the conservation of whole crop corn silage, untreated or treated with different LAB inocula, on the fermentation profile and on the aerobic stability of the silage. Corn was harvested at 42% dry matter and either not treated (control) or treated with Lactobacillus buchneri NCIMB 40788 (LB) at 300,000 cfu/g fresh matter (FM); Lactobacillus hilgardii CNCM I-4785 at 150,000 cfu/g FM (LH 150 ); L. hilgardii CNCM I-4785 at 300,000 cfu/g FM (LH 300 ); or LB+LH at 150,000 cfu/g FM each. In an attempt to experimentally simulate temperature fluctuations in the mass or at the periphery of a silage bunker, corn was conserved in laboratory silos at a constant temperature (20 ± 1°C; MASS) or at lower and variable outdoor temperatures (PERIPH; ranging from 0.5 to 19°C), and the silos were opened after 15, 30, and 100 d of conservation. Lactic acid, acetic acid, and ethanol contents increased in all the silages over the conservation period. The lactic acid content was higher (+10%) in the silages kept at a constant temperature than those conserved at the lower and variable outdoor temperatures. The acetic acid was higher in the treated silages than in the control ones conserved at a constant temperature for 100 d. Moreover, 1,2-propanediol was only detected in the treated silages after at least 30 d at a constant temperature, whereas only traces were detected in the LB+LH treatment for the other temperature conditions. The yeast count decreased during conservation at a slower rate in PERIPH than in MASS and on average reached 2.96 and 4.71 log cfu/g for MASS and PERIPH, respectively, after 100 d of conservation. The highest aerobic stability values were observed for LH 300 (191 h) in the MASS silage after 100 d of conservation, whereas the highest aerobic stability was observed in LB+LH (150 h) in the PERIPH silages. After 7 d of air exposure, a pH higher than 4.5 and a higher yeast than 8.0 log cfu/g were detected in all the silages opened after 15 and 30 d of conservation. A pH value close to that of silo opening was detected in the LB, LH 150 , and LH 300 silages conserved under MASS conditions after 100 d, whereas LB+LH was the most effective under PERIPH conditions. The temperature and its fluctuation during conservation of silage in laboratory silos influenced the fermentation, which in turn had an effect on the quality of silage and on the extent of the effect of LAB inocula.

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