For what purpose and how may humans use animals?

There is an increasing number of scientific findings that animals of many different species are conscious of suffering, have personality and are individuals. Moreover, they are conscious of desire, enjoy themselves and are doing as «useless» things as to play.

Assuming it is a mere question of time when we will be able to prove sentience, personality and playing in each and every species used by humans:
  • Which kind of uses are still acceptable for you personally?
  • Which kind of uses would you deem to be still acceptable for humanity as a whole?
  • How would you define «animal welfare»?
These are the questions the authors of this book have dealt with. After having sent in their contributions they were again confronted with the following question:

There is some evidence that plants, too, are sentient beings, have personality and are to be looked at as individuals. Supposed that this proves true for all plants mankind is using:
Which uses of plants are still acceptable? And does this alter your view on the question of using animals?