I don’t know the official reason Russia would send a dog into space but assume it was to see how an animal would fare in space.
Laika, a stray dog found in streets of Moscow apparently died from the capsule overheating. It has been 54 years since the death of Laika.
Despite the tragic loss of Laika, other dogs were sent into space by Russia. One can almost imagine what those dogs felt at takeoff when the spacecraft was thrust into space.
As far as I know the United States hasn’t sent an animal into space but that doesn’t mean it hasn’t happened.
Here’s hoping it never does happen.