Track 1-11

Description

The incidence of volatile organic compounds, including ethyl esters of lactic and acetic acids, in grass silages was evaluated based on a total of 620 samples from 10 different lab-scale ensiling experiments. These substances were detected after cold-water extraction by gas-chromatography. The correlations between ethanol and esters concentrations varied greatly depending on the trial. It was shown that ethanol concentration and pH of the silages affected ester formation. Low silage pH stimulated ester accumulation. Up to pH of 4.3, a stronger relationship between ethanol and esters contents was found than in grass silages having higher pH values. By allocating the silages to different ethanol classes it was shown that at up to 10 g/kg DM, the correlation between pH and total ester content was very weak (rS = -0.22). At > 10 g ethanol per kg DM, there was a strong negative relationship between the two tested parameters (rS = -0.82). Based on all available data (n = 1148) from different types of silages, a generally valid model is proposed to predict total ester concentrations (y) as a function of ethanol content (x): y = 114x (R2 = 0.76). It is recommended to use silage additives with proven record of reducing ethanol in silages, thereby minimizing the production of ethyl esters and excluding the potential negative effects of volatiles on feed intake.

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Novel Results on the Formation of Volatile Organic Compounds (VOC) in Silages

The incidence of volatile organic compounds, including ethyl esters of lactic and acetic acids, in grass silages was evaluated based on a total of 620 samples from 10 different lab-scale ensiling experiments. These substances were detected after cold-water extraction by gas-chromatography. The correlations between ethanol and esters concentrations varied greatly depending on the trial. It was shown that ethanol concentration and pH of the silages affected ester formation. Low silage pH stimulated ester accumulation. Up to pH of 4.3, a stronger relationship between ethanol and esters contents was found than in grass silages having higher pH values. By allocating the silages to different ethanol classes it was shown that at up to 10 g/kg DM, the correlation between pH and total ester content was very weak (rS = -0.22). At > 10 g ethanol per kg DM, there was a strong negative relationship between the two tested parameters (rS = -0.82). Based on all available data (n = 1148) from different types of silages, a generally valid model is proposed to predict total ester concentrations (y) as a function of ethanol content (x): y = 114x (R2 = 0.76). It is recommended to use silage additives with proven record of reducing ethanol in silages, thereby minimizing the production of ethyl esters and excluding the potential negative effects of volatiles on feed intake.