Dunno where you guys have been, but I posted this in the other thread back on 4 October. The USDA did in fact shut down 1 October, but Obama didn't do it. Congress did.
Letter to USDA from President of US
And no, they're not really essential. Each state has it's own Dept of Agriculture, partially staffed and funded by the federal government. Now, without the staff and funds from the federal government, each state must bear the burden alone. If you live in a state that produces little in the Agri market, no big deal. But if you live in a state like mine where 80+ percent of your products are from Agriculture, it can and will destroy the states budget.
So the question, is how long can the states hold out, before they have to shut down as well.