The Farmer's workshop is the workshop used for any jobs involving processing plants or animal products. It is built with any construction material, and it must be built by a dwarf with the Plant Processing, Milking, Shearing, Spinning, or Cheese Making labor enabled.
Gelding also occurs at a farmer's workshop. This is not a selectable menu option. Instead, animals designated to be gelded (on the Animals tab of Status screen) will automatically be assigned a gelding job at a farmer's workshop.
Labors: Plant processing, Milking, Shearing, Spinning, Cheese making