The effect of silo type and dry matter content on the maize silage fermentation process and ensiling loss

Abstract

To compare the fermentation process and ensiling losses in experimental silos and farm bunker silos (BS) and determine the correlation with the dry matter (DM) content at harvesting, maize forage was chopped and ensiled in four farms. Using similar harvesting and ensiling systems, one BS and 12 experimental silos were prepared in each farm; the latter consisted of three S100 silos (100 1 capacity with effluent discharge valve and no airtight sealing), three S500 pilot-scale silos (500 1 capacity with effluent discharge valve and airtight sealing) and six S002 micro-silos (2 1 capacity with airtight sealing and no effluent discharge valve). DM content of maize forage at harvesting varied from a minimum of 29.0% to a maximum of 38.3%, with important differences both among farms and among plots within the same farm (three plots per farm). Chemical characteristics of maize silage harvested in BS and in experimental silos were similar, but some differences in fermentation quality were observed. Experimental silos showed a more active fermentation, with higher production ( P < 0.01) of lactic acid (4.72%, 4.87% and 5.21% vs. 3.45% DM; in S100, S500, S002 silos and BS, respectively), acetic acid (1.43%, 1.30% and 1.40% vs. 1.03% DM) and ethanol (0.81%, 0.63% and 0.55% vs. 0.29% DM) than in BS, probably as a result of a lower degree of compression of the ensiled forage. S100 silos, with no airtight sealing, were characterized by a more heterolactic fermentation, showing a homolactic index (lactic acid to acetic acid + ethanol ratio) significantly lower than the other experimental silos and BS (2.12 vs. 2.62, 2.70 and 2.83; P < 0.01). Ensiling losses, measured on experimental silos, appeared to be higher in S100 silos than in S500 and S002 silos (DM loss was 5.3% vs. 3.3% and 2.6%, respectively; P < 0.05). Fermentation characteristics and ensiling losses were significantly correlated with DM content of maize plant at harvesting. The following regression equations were determined for the estimation of lactic acid concentration and DM loss of silage on the basis of initial DM content ( x, %): lactic acid (% DM)=10.384−0.171x±0.968; n=96; r0.725 DM loss (%)=292.24−16.48x+0.235x 2±2.90; n=48; r=0.679 S500 and S002 experimental silos appear to be useful devices to study the conservation of ensiled forage because they faithfully reflect the process that normally occurs in farm bunker silos.