I've been feeding the piggies in my garden, and they're not passing any piggy plop with seeds. Trid giving one 20 corn, and no plop, no seeds. Have the requirements changed?
In Ur corn does not grow in gardens or fields, it is harvested directly from the crops of chickens. You'll also find the piggies do not plop bean seeds because beans grow on trees that are raised from seasoned beans. Glitchian philosophers probably spend ages trying to decide which came first, the been tree, or the seasoned bean.
If you fed a piggy 3 or more of a single garden crop that's grown from seed (like corn) and there's no plop it must be a bug. File a bug report. BTW it's easiest to feed the piggies economically if you're carrying no more than 20 of the given crop when you go to feed them. With 20 or fewer on your Glitch you will get the option to give them exactly 3 each time you select Feed.
Piggies only plop seeds that can be planted in gardens. So if you want a plop, you'll have to stick to garden produce. Corn (maize) is a garden crop. Grain (wheat) comes from chickens.
I think they'll only plop if you feed them three crops one a time. The key to it is "one a time". (I've tried to feed them 30 of one crop to make it a faster process and there was no plop.
And some of us still can't see piggie plops! If you see in local chat that your piggie has plopped you probably have the "invisible plop" bug that I have., Friends can come in and examine them for you. Then you can pick up the seeds.