What is Ironic about their victory celebration?

There is little to celebrate. THere are casualties on both sides and the windmill is destroyed. To celebrate their victory, the pigs get drunk off a case of whiskey found in the cellar of the farmhouse. A few days later, the animals realize that they have remembered another Commandment incorrectly. It now read: "No animal shall drink alcohol to excess."

The main reason its ironic is because on one hand there are casualties and windmill is destroyed. On the other hand the pigs are getting drunk and when they are questioned, Squealer lies and explains that they heard it wrongly and the commandment was actually 'no animal shall drink alcohol...to excess'. The animals were fooled by the virtue of the pigs' intelligence and the animals' stupidity

What items do the pigs trade for with the humans ?what differences are there between these and those they traded for in earlier chapters ? Chapter 9