I always assumed there was no kindness tolerated towards our fellow sentient friends on whom we experiment in the field of biology, and no leniency towards the students objecting to hurting and killing them.  This Q&A on stack exchange (currently the greatest source of human knowledge, paired with wikipedia) gave me so much hope.  I’m sure it’s still gruesome and unavoidable for many students in many lab situations but this is well-reasoned coverage of compassionate options for the conscientious objector.