Why does Napoleon believe that he is dying the morning after he drinks the whisky?

In Chapter Eight of Animal Farm, the pigs find a crate of whisky in the cellar of the farmhouse and stay up late drinking. The next morning, "a deep silence hung over the farmhouse" and none of the pigs get to work on time. Worse still, Napoleon claims that he is dying and sends Squealer to inform the other animals.

In reality, this is the first time that Napoleon has ever drunk whisky and, being...

In Chapter Eight of Animal Farm, the pigs find a crate of whisky in the cellar of the farmhouse and stay up late drinking. The next morning, "a deep silence hung over the farmhouse" and none of the pigs get to work on time. Worse still, Napoleon claims that he is dying and sends Squealer to inform the other animals.

In reality, this is the first time that Napoleon has ever drunk whisky and, being a pig, he is not accustomed to alcoholic beverages. In short, he is suffering from nothing more than a hangover. Arguably, however, he does not want to admit this to the other animals because drinking alcohol contravenes the Seven Commandments.

For the other animals, however, Napoleon's claim is clear evidence of Snowball's treachery:

A rumour went round that Snowball had after all contrived to introduce poison into Napoleon's food.

It is interesting to note that Napoleon does not dismiss this rumour but he does change the relevant Commandment from "no animal shall drink alcohol" to "no animal shall drink alcohol to excess."