Actually, piggy feeders currently work without RH... Bug has been reported...here's hoping they don't fix this one, since it is cruel to have piggies die...
They are only 200 currants at an animal vendor...don't know if they are cheaper at auction.
Options include dropping food on the ground for your piggies before you leave the game...they should eat it. Piggies have also been known to nibble off fruit trees too...
Piggies will eat any food stuff left on the ground. A few tests ago, I put my piggy feeder in the cabinet and just left food on the ground just to test (ten piggies) if they would survive. I found all my piggies turned to meat when the next test came, and not all the food laid on the ground was eaten. I placed my piggy feeder back (and captured another 10 piggies), but logging in again after another test, some (but not all) piggies had kicked the bucket. My current setup now uses two piggy feeders (feeding 13 piggies), and so far I can happily say that I have had no piggy casualty since the last two tests. However, I've observed that the feeder's contents seem to decrease at a faster rate now. Either the piggies have gotten hungrier, or the devs must have tweaked something in the feeder's behavior.
In short, leaving food in the ground does not ensure that your piggies will survive between tests. A piggy feeder will, but I guess it depends on how many piggies you have. Oh, and I plan on buying a third piggy feeder, just in case (I have some RL matters to attend to :D and may not be able to log-in next test).