The story of Snowball is repeatedly altered by the regime. Regarding the "Battle of the Cowshed", Snowball goes from being a hero (First Class) to being, finally, on the human's side of the fight according to Napoleon and Squealer.
This is a pure manipulation of fact and of history where actual events are "reinterpreted" to a point that they become almost completely separate from reality. The facts become fiction and fiction takes the place of fact.
Another way to describe manipulative communication is persuasive techniques or propaganda. There are examples throughout the book. Sqealer is an expert at manipulation because he can twist anything. When he is faced with a challenge to his authority, he makes the pigs look good and the challengers look bad.
In addition to what the previous post says, Squealer uses manipulative communication to convince the animals that the pigs have not really broken the commandments (like the one about sleeping in a bed) and that the only choice the animals have is between doing everything the pigs' way and having Jones back. Both of these occur in Ch. 6.
Seeing that these are the sections of the text where there is greater consolidation of Napoleon's power, it is not surprising to see communication manipulated towards this end. Consider the sheep's bleating of "Four legs good, two legs bad" while Napoleon and Snowball argue about the state of the farm. This represents the manipulation of the animals' opinion to the extent that it is communicated to them that any disagreement with Napoleon is seen as representing the habits of "two legs" or "humans." The emergence of Minimus as one who creates songs that support the pigs also helps to represent manipulative communication. Squealer is the very embodiment of maniupulative communication as he is able to convince the animals that Napoleon was never against the building of the windmill. The assertion that Snowball is an enemy who works for Jones is another example of communication designed to manipulate the animals in that it takes their fear of Jones and projects it onto Snowball. Finally, the savagery shown by Napoleon in the seventh chapter is based off of the idea of manipulative communication. Animals are told to confess their crimes and no harm wil come to them, and in doing so, are savagely mauled to death by the dogs who go for the throats of the animals who confess.