Temperature during conservation in laboratory silos affects fermentation profile and aerobic stability of corn silage treated with Lactobacillus buchneri, Lactobacillus hilgardii, and their combination.

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 (LH150); L. hilgardii CNCM I-4785 at 300,000 cfu/g FM (LH300); 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 LH300 (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, LH150, and LH300 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.

Increase in aflatoxins due to Aspergillus section Flavi multiplication during the aerobic deterioration of corn silage treated with different bacteria inocula.

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 × 105 cfu/g of fresh matter (FM)], Lactobacillus hilgardii (LH) CNCM I-4785 (at 3 × 105 cfu/g of FM), or their combination (LB+LH; at 1.5 × 105 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 AFB1, AFB2, AFG1, and AFG2 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 log10 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 log10 cfu/g. The AF were found in both the fresh forage and at opening in all the samples, with a predominance of AFB2 (mean value of 1.71 µg/kg of DM). The inoculation 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 log10 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 log10 cfu/g, respectively, thus determining the ex novo production of AFB1 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 AFB1 production after silage opening.

Effects of conservation period and Lactobacillus hilgardii inoculum on the fermentation profile and aerobic stability of whole corn and sorghum silages.

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. © 2018 Society of Chemical Industry.

Leaching of S-metolachlor, terbuthylazine, desethyl-terbuthylazine, mesotrione, flufenacet, isoxaflutole, and diketonitrile in field lysimeters as affected by the time elapsed between spraying and first leaching event.

The effect of elapsed time between spraying and first leaching event on the leaching behavior of five herbicides (terbuthylazine, S-metolachlor, mesotrione, flufenacet, and isoxaflutole) and two metabolites (desethyl-terbuthylazine and diketonitrile) was evaluated in a 2011-2012 study in northwest Italy. A battery of 12 lysimeters (8.4 m(2) long with a depth of 1.8 m) were used in the study, each filled with silty-loam soil and treated during pre-emergence with the selected herbicides by applying a mixture of commercial products Lumax (4 L ha(-1)) and Merlin Gold (1 L ha(-1)). During treatment periods, no gravity water was present in lysimeters. Irrigation events capable of producing leaching (40 mm) were conducted on independent groups of three lysimeters on 1 day after treatment (1 DAT), 7 DAT, 14 DAT, and 28 DAT. The series was then repeated 14 days later. Leachate samples were collected a few days after irrigation; compounds were extracted by solid phase extraction and analyzed by high-performance liquid chromatography and gas chromatography-mass spectrometry. Under study conditions, terbuthylazine and S-metolachlor showed the highest leaching potentials. Specifically, S-metolachlor concentrations were always found above 0.25 µg L(-1). Desethyl-terbuthylazine was often detected in leached waters, in most cases at concentrations above 0.1 µg L(-1). Flufenacet leached only when irrigation occurred close to the time of herbicide spraying. Isoxaflutole and mesotrione were not measured (<0.1 µg L(-1)), while diketonitrile was detected in concentrations above 0.1 µg L(-1) on 1 DAT in 2011 only.

Aerobic stability of maize silage stored under plastic films with different oxygen permeability.

BACKGROUND: The most important factor that can influence silage quality is the degree of anaerobiosis maintained during conservation. The quality of the plastic film is a key factor, since the permeability of polyethylene to oxygen is too high for silage conservation. The aim of this work was to assess the effects of the interaction between three plastic films with different degrees of oxygen permeability and two different maize silage conservation times on fermentation, microbial quality and aerobic stability. RESULTS: The conservation time affected the pH, lactic and acetic acids, 1,2-propanediol and lactic/acetic acid ratio, with higher pH, lower lactic acid concentration and lactic/acetic acid ratio but higher acetic acid and 1,2-propanediol concentrations being found in silages conserved for 110 days versus silages conserved for 55 days. The plastic film affected the pH, lactic and acetic acids and lactic/acetic acid ratio. The yeast count was lower and aerobic stability higher for silage conserved under the oxygen barrier film for both conservation periods. CONCLUSION: The positive interaction between length of storage and the increased anaerobiosis of silage during conservation provided by the oxygen barrier compared with polyethylene film helped reduce the yeast count and increase the aerobic stability of maize silage, even when less acetic acid was produced during ensiling.

Buffer strip effect on terbuthylazine, desethyl-terbuthylazine and S-metolachlor runoff from maize fields in Northern Italy.

The effectiveness of a 6 m wide vegetative buffer strip for reducing runoff of S-metolachlor, terbuthylazine and desethyl-terbuthylazine was studied in 2007-2008 in Northern Italy. Two cultivated fields, with and without the buffer strip, were compared. Residues of the chemicals were investigated in runoff water collected after runoff events and their dissipation in the soil was studied. The highest concentration of the chemicals in water occurred in samples collected from the unbuffered field at the first runoff events. Losses of terbuthylazine and S-metolachlor in runoff waters were particularly high in 2007 (2.6% and 0.9% of the amount applied, respectively). Soil half-life of terbuthylazine and S-metolachlor ranged between 12.1 and 8.9 days and 16 and 7 days, respectively. The presence of desethyl-terbuthylazine was related to parent compound degradation. The buffer strip allowed an important reduction of chemical content in water (> 90%), in particular during the first runoff events.

Dissipation of propanil and 3,4 dichloroaniline in three different rice management systems.

This study focused on the dissipation of propanil and 3,4 dichloroaniline (3,4 DCA) over time in the soil, field water, inlet water, and outlet water of paddy fields under three management systems: conventional water seeding (CON), conventional water seeding with supplied liquid manure (LMA), and dry seeding (DRY). Propanil dissipation in water was also investigated under laboratory conditions. The field study was conducted from 2004 to 2006 at Vercelli, northern Italy. Propanil and 3,4 DCA showed rapid dissipation in water and soil environments both in the field and in the laboratory. Under controlled conditions, chemical hydrolysis was not detected for either compounds for up to 100 d at pHs of 5, 7, and 9. In the laboratory, the half-life of propanil in irrigation water was 1.1 d; its half-life in soil was routinely measured at <1.0 d (between 0.17 and 1.77 d). 3,4 DCA was found to persist much longer. Measured in all three study years at 50 d after treatment, its concentration ranged between 44 µg kg (CON) and 140 µg kg (DRY). Propanil and 3,4 DCA concentrations in paddy water were particularly high in samples collected at 4 d (2004) and 2 d (2005) after treatment. Maximum concentrations were 54.4 µg L (CON) for propanil (2005) and 113.7 µg L (LMA) for 3,4 DCA (2004). The concentrations of propanil and 3,4 DCA in inlet water were never above 1.1 and 0.3 µg L, respectively, whereas the highest concentration of each compound in outlet water was in samples collected first after treatment in 2005 and 2006. Both chemicals dissipated rapidly in all the soil-water environments but displayed no important differences among the three management systems. In conclusion, propanil and 3,4 DCA did not persist longer in paddy fields. A risk of water network contamination by these compounds may occur only early after herbicide spraying. A water-holding period after herbicide spraying may reduce this risk.