Orwell mostly uses chapter 6 as a series of foreshadows. The first involves, of course, Napoleon. This time he's beginning to trade with the neighboring farmers, Foxwood and Pinchfield. The necessity comes from materials only humans can make. But the picture-perfect world the animals imagined had no conflicts like this. I mean, who could have imagined that Boxer might need new horseshoes? Well, ok maybe the animals were being naive. Anyway, Napoleon decides that he will conduct trade with the "outside" world. But some of the animals think that maybe this was once forbidden.
Orwell explains, "Once again the animals were conscious of a vague uneasiness. Never to have any dealings with human beings, never to engage in trade, never to make use of money— had not these been among the earliest resolutions passed at the first triumphant Meeting when Jones was expelled? All the animals remembered passing such a resolution; or at least they thought that they remembered it. The four young pigs who had protested when Napoleon abolished the Meetings raised their voices timidly, but they were promptly silenced by a tremendous growling from the dogs."
Soon the animals have more reason to be uneasy. They notice that the pigs have recently begun to sleep in beds, which, of course, is one of the forbidden associations with humans. Muriel reads the commandments to the confused Clover from the barn wall and notices that one of them has been altered. Now it reads, "No animals shall sleep in a bed with sheets."
Again Orwell explains, "Curiously enough, Clover had not remembered that the Fourth Commandment mentioned sheets; but as it was there on the wall, it must have done so." Of course, Clover, the unsuspecting loyalist of Napoleon, simply thinks that everything is innocent.
Toward the end of the reading, the windmill, which was Snowball's idea stolen by Napoleon, mysteriously collapses in the middle of the night. Of course all the animals are upset that such a terrible event could make worthless the object for which they had labored so long. Napoleon and Squealer completely blame Snowball with no hesitation.