Aerobic deterioration of silage
When the silo is opened for feeding the silage is exposed
to aerobic conditions that lead to its deterioration [13]. A
similar situation occurs if the silage is poorly packed or the
silo face is poorly managed and air enters the silo.
Indicators for these spoilage processes are increasing
temperature and pH, dry matter losses, loss of nutrient
availability, surface mold growth and feed refusal by the
animal. Aerobic deterioration of silage is caused by rapid
increases of yeast and mold flora that oxidize lactic acid
and volatile acids and result in increased temperatures
and pH [5].
Weinberg et al. [14] investigated several homofermentative
lactic acid bacteria for their potential on aerobic
stability when used as silage inoculants. The inoculated
silages tended to spoil even faster than the control silage.
Homofermentative fermentation is more efficient and uses
less water-soluble carbohydrates (WSCs) than heterofermentative
fermentation. The high residual water-soluble
carbohydrates and lactic acid and the lack of volatile fatty
acids were associated with aerobic deterioration. Aerobic
spoilage was attributed mainly to high yeast activity.
Danner et al. [15] investigated the effect of different
compounds formed by heterofermentative lactic acid
bacteria on aerobic stability of silage. Aerobic stability
was directly correlated to the amount of acetic acid present
in silages. Acetic acid acts as growth inhibitor on spoilage
organisms by decreasing the maximum growth rate and
therefore acetic acid increases the aerobic stability
exponentially. Only butyric acid has a comparable effect
whereas lactic acid, 1,2-propanediol and 1-propanol had no
effects. Figure 1 shows a high correlation of the different
compounds with the aerobic stability, which indicates that
acetic acid was the sole parameter influencing the aerobic
stability of silages under comparable conditions.
The major challenge for modern silage inoculants is to
obtain a certain level of acetic acid in fermented forage.
This is a completely new concept because, until recently,
acetic acid was primarily associated with the activity of
clostridia, which are not desirable in silages.
Aerobic deterioration of silageWhen the silo is opened for feeding the silage is exposedto aerobic conditions that lead to its deterioration [13]. Asimilar situation occurs if the silage is poorly packed or thesilo face is poorly managed and air enters the silo.Indicators for these spoilage processes are increasingtemperature and pH, dry matter losses, loss of nutrientavailability, surface mold growth and feed refusal by theanimal. Aerobic deterioration of silage is caused by rapidincreases of yeast and mold flora that oxidize lactic acidand volatile acids and result in increased temperaturesand pH [5].Weinberg et al. [14] investigated several homofermentativelactic acid bacteria for their potential on aerobicstability when used as silage inoculants. The inoculatedsilages tended to spoil even faster than the control silage.Homofermentative fermentation is more efficient and usesless water-soluble carbohydrates (WSCs) than heterofermentativefermentation. The high residual water-solublecarbohydrates and lactic acid and the lack of volatile fattyacids were associated with aerobic deterioration. Aerobicspoilage was attributed mainly to high yeast activity.Danner et al. [15] investigated the effect of differentcompounds formed by heterofermentative lactic acidbacteria on aerobic stability of silage. Aerobic stabilitywas directly correlated to the amount of acetic acid presentin silages. Acetic acid acts as growth inhibitor on spoilageorganisms by decreasing the maximum growth rate andtherefore acetic acid increases the aerobic stabilityexponentially. Only butyric acid has a comparable effectwhereas lactic acid, 1,2-propanediol and 1-propanol had noeffects. Figure 1 shows a high correlation of the differentcompounds with the aerobic stability, which indicates thatacetic acid was the sole parameter influencing the aerobicstability of silages under comparable conditions.The major challenge for modern silage inoculants is toobtain a certain level of acetic acid in fermented forage.This is a completely new concept because, until recently,acetic acid was primarily associated with the activity ofclostridia, which are not desirable in silages.
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