Hi Gowin,
Your tag is correct, but I usually use shop=agrarian
It is simpler and seems more commonly used:
https://taginfo.openstreetmap.org/tags/shop=agrarian
Also mentioned in the trade tag page:
https://wiki.openstreetmap.org/wiki/Tag:shop%3Dtrade
Someone also suggested shop=animal_feed. That would be more accurate, but is not much used (23 only...).
Cheers,
Totor