Influence of different slurry application methods on grass silage quality

When slurry is applied, a great number of bacteria (e. g. clostridial spores) are spread on both the soil and forage. An experiment conducted at Agroscope Tänikon in 2013 and 2014 investigated the influence of three different slurry application techniques (broadcast, band-spread and trailing-shoe) on silage quality. In both years, samples were taken of three different cuts (in 2013, puregrass sward; in 2014, mixed grass-clover sward). The forage was pre-wilted and ensiled in laboratory silos. Besides dry matter and nutrient content, clostridial spores were also determined in the fresh forage. With the silages, in addition to the most important nutritional parameters, special focus was placed on butyric acid content, in order to determine the influence of the individual slurry application methods. Although the 2013 forage samples exhibited low counts of clostridial spores, somewhat higher clostridial spore counts were determined in 2014. Despite the low number of clostridial spores, differences were detected between the various treatments. For the two treatments broadcast and band-spread, there were slightly higher counts for the late slurry application date than for the early date. Furthermore, there were indications of a negative influence of the thicker as opposed to the thinner slurry. Nevertheless, the correlation between the clostridial spore count in the forage and the butyric acid content in the silages was very low. The degree of pre-wilting of the forage as well as the age of the forage respectively the crude-fibre content at the time of ensiling were vital factors for silage quality.

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