Bechoros 2

Does non-Jewish ownership of the mother or fetus preclude the consecration of the first born animal? • According to Rashi and Tosafos, when buying an animal from a non-Jew, what consecration is achieved and why? • When and why is selling a large domesticated animal to a non-Jew prohibited? • Why is the longstanding custom to be lenient? • Is it permitted to sell the rights to future progeny of a non-gravid cow to a non-Jew?