You'd feel better if there were people in the pictures and the gates weren't locked?
If you're that concerned, they offer opportunities to tour the farms. Wal-mart in China also offers opportunities to buy their pork. So there's a great vacation for you. Tianli gives you lunch on the tour, and then you can cook your own pork for other meals. Now you just need to figure out where to stay.
A while back there was a pork scare in China. Some chemical was used by one of the producers. Whatever it was, it must have been bad. Lead in toys, no problem. Asbestos in drywall, who doesn't use it? But this chemical in pork was a media frenzy, with man on the street interviews asking shoppers if they were afraid to buy pork now. Tianli - which usually is about as bad as passing along info as any other Chinese company - actually put out three press releases in the span of about two weeks, saying they don't use this chemical, they welcome any regulatory oversight, etc (the Chinese at one point were thinking about doing urinalysis on pigs). You'd think in all that, the Chinese government would have figured out that these farms didn't actually have any pigs if that was the case.
The chemical is clenbuterol, which increases muscle mass - it's widely used in China. OINK would get a lot of attention from inspectors / regulators being a publicly listed company, so they would have been uncovered by now if they were using clenbuterol. Plus, Walmart would have had inspectors there if they are selling their pork.