"Director, why not pair Jiaojiao with Ice Cake directly without waiting for Ice Cake to grow up?"
Fang Ye saw the barrage and explained, "Ice Cake is a Bengal tiger, Jiaojiao is an Amur tiger, so it's impossible to pair them up. That would contaminate the gene pool. It's the same principle as mating blue peafowl with green peafowl.
Moreover, Jiaojiao has been guarding Ice Cake as she would her own cub, and Ice Cake has always seen Jiaojiao as a mother. Even if Ice Cake grows up, it's very likely that the spark won't be there; he would lack attraction.
For us humans, inbreeding presents severe ethical problems—actually, it might not just be due to our upbringing but an instinctual defensive mechanism in our genes.
Animals also tend to avoid inbreeding, especially our close relatives in the primate family.
For example, macaques practice polygyny, where a female will mate with multiple males at the same time, making it hard to determine who the father is.