What reason does Squealer give for the pigs taking all the apples and milk?

He said that they do important work and need to maintain their health. They do not even like milk, but are willing to make the sacrifice for the good of everyone on the farm.

'Comrades!' he cried. 'You do not imagine, I hope, that we pigs are doing this in a spirit of selfishness and privilege? Many of us actually dislike milk and apples. I dislike them myself. Our sole object in taking these things is to preserve our health. Milk and apples (this has been proved by Science, comrades) contain substances absolutely necessary to the well-being of a pig. We pigs are brainworkers. The whole management and organisation of this farm depend on us. Day and night we are watching over your welfare. It is for your sake that we drink the milk and eat those apples. Do you know what would happen if we pigs failed in our duty? Jones would come back! Yes, Jones would come back! Surely, comrades,' cried Squealer almost pleadingly, skipping from side to side and whisking his tail, 'surely there is no one among you who wants to see Jones come back?'

Actually,not just because they work the hardest but the pigs are also one of the leaders right after Napoleon .In the book,Squelar says to everyanimal on the farm that "We pigs are brainworkers.The whole management depends on us.Day and night,we are watching over your welfare (continues on chapter 3,sorry i dont remember the second part ) .I HOPE THIS HELPS U VER MUCH (: