This has previously been achieved, of course, in such fictional porcine adventures as “Babe” and E.B. White’s “Charlotte’s Web.” Shorn of any humanized fantasy, “Gunda” arouses protective sentiment merely by showing the pigs’ drab everyday routines, which turn oddly riveting at close quarters, as the piglets grow, play, guzzle and instinctively separate into ranks — with one forlorn runt left lagging.