Changes in chemical composition and fermentation profile in silages from rehydrated grains of maize hybrids during prolonged air exposure

Most studies investigated the effects of air exposure during the ensiling of whole maize silage and high-moisture maize grains on the chemical composition and fermentation profile, but not of rehydrated grain. The aim of the present study was to investigate the effect of the hybrid and the duration of air exposure on the pH and the content of moisture, main nutrients, fermentation products and nitrogen fractions in silages from three commercial maize hybrids. The grains were rehydrated to 32 % of moisture and ensiled for 63 days with the addition of an inoculant (BIO-SIL®, Dr Pieper Technologie und Produktentwicklung GmbH). After opening, the silages were stored at room temperature for 10 days and samples were taken after 0, 1, 3, 5 and 10 days of air exposure. With increasing duration of air exposure, the content of moisture, lactic and acetic acid and ethanol decreased, while the pH value and the content of water-soluble carbohydrates and ammonia increased. The hybrid affected all the determined properties of the silages except the pH and the ethanol content. There were distinct differences in the contents of moisture, total sugars, water-soluble carbohydrates, lactic, acetic, propionic and isobutyric acids, methanol and ammonia, suggesting that some hybrids may be more susceptible to aerobic spoilage. The majority of the properties remained similar until the fifth day of air exposure, suggesting that the silages of all three hybrids were stable during this period. The only property that increased immediately after air exposure was the content of nitrogen fractions suggesting that proteolysis was occurring, even though pH and lactic acid content remained unchanged. Overall, the results of the study indicate that the behaviour of rehydrated maize silage after exposure to air should be taken into account when selecting maize hybrids.