I came across this article
, and must say I'm puzzled. African and Asian lions were interbred to create 'hybrids' in the 70's and 80's, they turn out to be sickly and prone to disease, and are being let die off. It really surprises me that a hybrid like this would be so vulnerable; mules, for instance, are quite hearty, which is why we have them. It also surprises me that they can breed at all: such hybrids are generally sterile.
It would make more sense to me if they just started breeding them back in with the pure lines, diluting the unsuccessful mix but perhaps retaining some of the introduced variety that you expect to be helpful. That's what bothers me: genetic variation should be good for the animals. I wonder what's up that has been left out of that article.