At a recent evening event at the zoo "Animal Question Time" it was mentioned that in some cases where cubs have been still born or died soon after birth (not necessarily at Edinburgh Zoo) tests have shown that they showed signs of congenital heart problems. This appears to be a problem within the capitive population of Asiatic lions as a whole rather than one particular zoo. There also seems to be evidence to suggest that the lionesses seem to be able to pick up on a problem very early on. Rather than put a lot of effort into a cub that might not survive or weaken the gene pool they take iton themselves to kill the cubs and, as with any species, having a dead animal lying around would give away their location by scent, the young get eaten. To me this doesn't suggest bad parenting at all, if correct. Quite the opposite, this, to me, suggests quite remarkable and highly skillful managing of the species, albeit in an artificial environment.