Mowing alfalfa in wide swaths markedly reduces the amount of time the crop must wilt before it can be chopped for silage, but under good conditions the resulting silage is generally not improved, say University of Delaware researchers.

Dairy scientist Limin Kung and his colleagues mowed alfalfa leaving narrow and wide swaths for three consecutive cuttings. Using a mower-conditioner with a 13’ cutting width, they made narrow swaths ranging from 4 to 5’ wide (30-37% of cutterbar width) and wide swaths ranging from 8 to 9’ wide (62-67% of cutterbar width). They collected samples from windrows and monitored moisture content until a target of 43-45% dry matter was obtained. Forage from random windrows was harvested by hand, chopped through a forage harvester before being packed in vacuum-sealed bags, and allowed to ensile for 65 days.

They report that, over all cuttings, the resulting dry matter content was almost identical between narrow- and wide-swath silage. However, the hours of wilting time needed to reach the targeted dry matter for narrow- compared to wide-swath silage in cuttings one, two and three were 50 vs. 29, 54 vs. 28 and 25 vs. 6, respectively.

At the time of ensiling, the wide-swath silage had more water-soluble carbohydrates (5.1%) than the narrow-swath silage (3.7%), and a lower pH, but fermentation was similar. Wide swathing didn’t affect the concentration of ash or the digestibility of NDF, but it lowered the N content slightly and increased the ADF of the resulting silage by about one percentage point, say the researchers.