I remember a year or two back talk of attempting AI with the 2 elephant cows at WMSP because the bull was not considered to be mature enough to successfully mate with them .
He's big enough to cover them now, or so I got told when I visited. Just a case of wating now, as the females won't let him "finish the job" so to speak
I'd be more worried about the females at WMSP killing their calves. Seeing as they were hand reared themselves, I think it's quite common for hand reared elephants to kill their young at birth.