Mustarrd Seed Extraction

This year we planted a lot of mustard to follow on from the potatoes as we have chickens and they love the leaves.
However, the mustard has now run to seed. Is there a reasonably efficient mechanical way (other than by hand) to extract the seed?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.