Any tips for splitting nails?

I have three beautiful, happy and healthy Jack Russells. One of my boys, Trevor aged seven, has always loved chasing a ball. My problem is that every now and then he must land awkwardly having jumped to catch his ball, and splits a nail. This isn't just when ball chasing, it can also happen if running on uneven ground, such as rough moorland or around rock pools at the seaside. It is not always the same nail or same foot. Obviously when this happens it's very painful for him and bleeds quite badly for a few seconds. My vet has confirmed that Trevor (and his nails) are in tip top condition, and has come to the conclusion that poor Trev is just unlucky and maybe his stopping/landing techniques are to blame. I wondered if cod liver oil might help, but as my boys are fed a top quality complete food with some BARF, I don't want to over do the vitamin A, or anything else. My other two boys Graham and Wilf never have any such trouble. To put this in perspective, my boys get daily long walks and plenty of exercise in varied locations. This nail problem only occurs maybe about twice a year so I can't say it's frequent. It's just that being so distressing for him (and me!) I wondered if anyone had any ideas. He definitely won't wear those doggy boots!
Many thanks
Sara Marlow, Huddersfield

Richard Allport, alternative vet, says...
It seems unlikely to me that Trevor is just awkward at landing, and even if the nails look fine, I’m pretty sure there must be some weakness in them. Supplements of Zinc and Biotin will help strengthen the nail. Give them a try and see if Trevor can avoid his ‘split ends’!