An example of dramatic irony in George Orwell's "Animal Farm" is that the reader knows that the money the pigs received from selling the loyal and hardworking horse Boxer to slaughter has been spent on whiskey, but the other characters do not. This type of irony, wherein the reader is aware of crucial facts which the characters are ignorant of, is a commonly used device in Orwell's novel.
Writers often use dramatic irony in order to build suspense and heighten tension. Statements made by characters (for example, characters who unwittingly make what the readers know to be disastrous decisions) take on a very different resonance as the result of dramatic irony. This literary device puts the reader in a position of superiority to the characters and provides them with a different lens through which to view the actions of the plot.
The novel Animal Farm is a satire of political events in Russia. Orwell was a harsh critic of Joseph Stalin and wrote the novel in response to what he believed to be the emergence of a brutal dictatorship. Instead of writing directly about the situation, he created an allegory wherein he set the story on the titular farm and made all of the characters animals.