A fat pig is as good as an elephant, but its nose is short. Kill one head for the entire society, enough to feed you for half a year. What does that mean?

It is an extreme exaggeration to describe pigs as being raised big and fat.

This is a limerick written during the Great Leap Forward period, reflecting the "exaggerated style" at that time.

There is another song:

A grain of rice can be used to cook a pot, and a corn can be used to pull a cart; sorghum stalks are used to build wires, and melon rinds are used to cross the Yellow River.