Effect of harvest time on fermentation profiles of maize ensiled in laboratory silos and determination of drying losses at 60°C

Abstract

The objectives were to investigate the effect of premature ensiling of maize on alcohol fermentation in laboratory silos and the loss of fermentation products and glucose in silage following drying at 60°C for 48 h. During four consecutive weeks maize was harvested and ensiled for 60 days in vacuum-sealed laboratory silos. The content of DM in silage increased (p<0.001), whereas acetate and ethanol decreased (p<0.01) with later time of harvest. Concentrations of methanol and propanol were generally <1 g/kg DM and the content of 2-butanol <0.03 g/kg DM. The content of D-glucose was lower (p=0.03) in silage harvested the second week compared with the other harvest times (40.9 vs. 66–69 g/kg DM). Overall, silage pH was negatively correlated with L-lactate (r=−0.93). Drying increased pH, butyrate and valerate, although the numerical effect was small. A major portion of acetate was lost in drying, and the D-glucose content was reduced by approximately 45% after drying. Alcohols and esters were completely lost in drying. We conclude that ensiling of pre-mature maize does not lead to extensive alcohol fermentation in laboratory silos following 60 days of ensiling, and that dry matter correction based on fermentation products determined in dry samples may be erroneous due to inability to predict wet sample content from samples dried at 60°C.

Keywords:

• Maize silage
• harvest time
• alcohol fermentation
• drying loss

Acknowledgements

We acknowledge the contribution of our technicians and colleagues, Birgit H. Løth (laboratory analysis), Torkild N. Jakobsen (sample preparation), Inger Balthzersen, Peter S. Sørensen (ensiling), Karsten Jensen (silage sampling) and Uffe Schmidt (maize harvest).