The answer to this question depends on at what point during the novel you are referring, although arguably the animals' quality of life stay roughly the same throughout.
In the beginning, life under Mr. Jones' rule is not good. He forgets to feed the animals, and they work hard all week, with only one day off. Once the rebellion occurs, the animal's quality of life improves temporarily, as their spirits are lifted with the idea of doing all the work for their own (not human) benefit. Soon, however, the pigs take over, and the animals' quality of life eventually becomes worse than when they were under Jones' rule, since they find themselves at the end of the book with zero days off, among other hardships. The only animals which enjoy an improvement in life quality are the pigs.
This all makes sense when one considers Orwell's purpose in writing this book as an allegory for the Russian Revolution: his theme maintains that rebellions do not result in a better life because eventually a new group will take power and become corrupted by it.