It's a parody of Soviet style socialism, with its political elite (pigs) - the 70's cartoon alone cannot do justice to Orwell's lifelong habit of lambasting socialism/socialists. Animal Farm is quite a clever book on some levels.
I think you've got your wires crossed there Shameless, my reply was to Natchrawldrys question about A Serbian Film. As for Animal farm, it's one of the greatest political satires ever written, the cartoon was just a sensible way to get the message over to the masses, especially kids, but if similar had been done in the USSR or China decades ago ribbing capitalism or free speech, we'd all say it was just brainwashing.