For something like this they would certainly only use female elephants that are in the optimum reproductive age as carriers. These would have to be taken out of any normal elephant breeding programmes during the attempts. That means they would need 10s of females and these would have to be kept under highly controlled conditions. Where are they going to get that many female elephants that are in the optimum reproductive age?
That post was very interesting. I do have a solution for this one though, although a bit controversial. Kruger National Park have been permitted to cull their elephants, maybe animals could be taken from the wild for this? I know we generally don't take animals from the wild, but if they're being culled anyway maybe it's a better solution?