I've never had a problem with does eating the babies. Tho my doe will sometimes eat one that died - but that's rare. I would guess lack of protein. Was your friend feeding pellets? And feeding enough? I start free feeding about a week or 2 before the babies are due & continue until they are weaned. When my dad's rabbitry was at its largest - about 60 does - I don't remember him loosing any babies to the doe eating them.
Another question - was he sure it was the doe eating the babies? Depending on the type of cage, could have been rats.
And I agree with Haverwilde - if there is sufficient food & sufficient protein & the doe still eats the babies - time to cull.
Mr. Bingley - with the good ol' American diet, it's impossible to suffer from rabbit starvation. I cook with butter & olive oil, we eat beef whenever we can afford it, every so often chicken, & lots of eggs. I've noticed that if we eat no meat but rabbit, we get tired of it. I start craving beef. Variety is the spice of life.
Rabbit starvation & trout starvation are more apt to happen in survival situations. Neither have enough fat to sustain life for more than a few weeks. And what fat there is on rabbits is nasty. Somewhere I read that part of the problem is the energy expended in catching those rabbits & trout; too much energy out & too little coming in.
The biggest drawback to having rabbits - beside the need to butcher them - is all those dinky bones.
Speaking of butchering - I finally have the proper tools. A while back I bought a Victorinox rabbit knife & a pair of Gerber kitchen scissors. Pricey but worth it. I also finally learned how to tie a slip knot so I can hang the bodies with shoelaces for butchering. I used to use wire but with my wimpy fingers, my husband had to put the rabbit up & take it down for me. He's glad to be out of one more job!