Is there an encyclical on animal testing/rights?
There are none because ‘animal rights’ is generally a buzzword used by secular humanists to lower human rights rather than elevate animal rights. Having said that, cruelty to animals is gravely disordered and good Catholics are called to be good stewards of God’s gift of creation and nature including and especially animals. St. Francis of Assisi was a great model for everyone (not just Catholics) to follow in terms of our relationship not just with God and with each other, but with animals and the rest of nature.
