Effects of air exposure, temperature and additives on fermentation characteristics, yeast count, aerobic stability and volatile organic compounds in corn silage

Abstract

Ensiling conditions strongly influence fermentation characteristics, yeast count, and aerobic stability. Numerous volatile organic compounds including esters are produced, which may negatively affect feed intake and animal performance and air quality. In addition to a farm survey, 3 laboratory experiments were carried out to study the effects of air (by delayed sealing or by air infiltration during anaerobic storage), temperature (20 and 35°C), and various types of additives [blends of either sodium benzoate and sodium propionate (SBSP) or of sodium benzoate and potassium sorbate (SBPS); buffered mixture of formic and propionic acids (FAPA); homofermentative inoculant (LAB)]. After additive treatment, chopped whole corn plants were packed into 1.5-L glass jars and stored for several months. For treatments with air infiltration, glass jars with holes in the lid and body were used. The farm survey in 2009 revealed large variation in lactate, acetate, ethanol, n-propanol, and 1,2-propanediol concentrations. Whereas ethyl esters were detected in all silages, the mean ethyl lactate concentrations were higher than those for ethyl acetate (474 vs. 38mg/kg of dry matter). In the ensiling experiments, few unequivocal effects of the tested factors on the analyzed parameters were observed due to many interactions. Delayed ensiling without additives decreased lactic acid production but, in one trial, increased acetic acid and had no effect on ethanol. The effect of delayed sealing on yeast counts and aerobic stability differed widely among experiments. Air infiltration during fermentation tested in one trial did not alter lactic acid production, but resulted in more acetic acid in delayed and more ethanol than in promptly sealed untreated silages. Greater ethanol production was associated with increased yeast numbers. Storage at high temperature resulted in lower lactic acid and n-propanol, and a trend toward reduced ethanol production was observed. The additive FAPA consistently caused increased ethanol and reduced n-propanol levels with no effect on yeast counts and aerobic stability. When the additives SBSP and SBPS decreased n-propanol and ethanol, reduced yeast counts were also found. Ethyl ester formation was strongly correlated with those of ethanol and to a lesser degree with those of the respective acid.

Effect of compaction, delayed sealing and aerobic exposure on maize silage quality and on formation of volatile organic compounds

“…Weiss et al. () suggested that ethyl ester can also be directly produced by lactic acid bacteria (Liu & Siezen, ) or yeasts (Fredlund, Druvefors, Olstorpe, Passoth, & Schnürer, ; Nordström, ) and not only by the esterification of ethanol with a fermentation acid. They stated that it seems very likely that both chemical and biochemical processes are involved in forming esters.…”

“…When these silages were exposed to air after opening, both ethyl ester concentrations decreased during exposure. Also, both ethyl esters showed a strong correlation with ethanol, highlighting the prominent role of ethanol in esterification (Weiss & Auerbach, ; Weiss et al., ). The immediate sealing of a silo leads to suppression of yeast growth.…”

Silage fermentation—updates focusing on the performance of micro‐organisms

“…The factors affecting the extent of aerobic deterioration act together in a complex process whereby interactions between the significant diversity of micro‐organisms can cause many variations (Weiss et al . ).…”

Ensiling in 2050: Some challenges and opportunities

“…In developed countries, nitrogen oxide (NO x ) emissions from fertilizer and manure accounted for 27% of GHG emissions and CO 2 from all farm sources accounted for 21% of GHG emissions. Weiss, Kroschewski, and Auerbach (2016) and Brüning, Gerlach, Weiss, and Südekum (2018) found that elevated concentrations of VOC were associated with delayed silo sealing which was accompanied by increased ethanol and yeast counts. Differences in methods of crop storage did not appear to be specifically addressed in that analysis.…”