Argument: Animals experience pain and suffering in experiments
Dr. Hadwen Trust - "6. Do animals suffer in experiments? Yes, an experiment on a living animal only needs to be licensed by the UK government if it has the potential to cause “pain, suffering, distress or lasting harm.” (see the Animals (Scientific Procedures) Act 1986). Animals are capable of experiencing both physical pain and suffering as well as psychological harm like fear (including, for some species, anticipation of harm), boredom or depression. Suffering can be caused not only by the experimental procedure, but also due to the unnatural and often stark laboratory environment, handling or excessive noise or light.
[...]Beyond physical pain, animals can be harmed by confinement, frustration, fear, isolation, and loss of life – experiences unavoidable for animals confined in laboratories and used in experiments. The Dr Hadwen Trust does not believe that animal experiments are ethically supportable."
Christian Barnard, surgeon - "I had bought two male chimps from a primate colony in Holland. They lived next to each other in separate cages for several months before I used one as a [heart] donor. When we put him to sleep in his cage in preparation for the operation, he chattered and cried incessantly. We attached no significance to this, but it must have made a great impression on his companion, for when we removed the body to the operating room, the other chimp wept bitterly and was inconsolable for days. The incident made a deep impression on me. I vowed never again to experiment with such sensitive creatures."