I have 2 californians does and a NZ/Papillion buck. In general I find that when I grow them all out to week 12, they eat 9/10th of a 20kg bag of 17% protein rabbit pellets, this includes the feed for the adults.
I wean at 64 days when I remate the doe, and that is the point when I process the bucks because they don't grow as well as the females (and are harder to peel!) and in any case, 8 weeks is the sweet spot in terms of feed efficiency because nothing fattens a bun more than the does' milk. Also, the cage space does not come free either and the small rabbits are far easier to clean too. Since I have no recorded the feed for the maternity cage, I will do this for the upcoming litter, should be fun
My supplier had only 14% feed once, and so I tried it. The result was a greatly reduced growth rate of the kits and both does' next litter was fewer and lighter.
Feed conversion is a voodoo measurement, because it does not take into account the fluid in the food. Hence Tilapi has a 2:1 conversion, because fish flakes are somewhat dry Personally I think the protein/fat/carb intake is a better measure.
But really, unless you go past the rapid growth curve in any meat breed of any animal, what you feed is fairly much what you get -- which in my case is 900gm for an 8 week old buck, and 1.6kg for a 12 week old doe. If I let a buck grow to 12 weeks, they tend to have 1.4kg carcasses, and I can taste the buck taste, even after removing all the glands. (I weigh without innards)
Trivia fact: the best dress out percentage is achieved by Dutch rabbits @8 weeks, who are rather small. http://msucares.com/livestock/small_animal/slaughter.html
Dressing Percentage of New Zealand and Dutch Rabbits at Different Ages
Age New Zealand Dutch
8 weeks 55.9% 60.3%
13 weeks 59.2% 63.3%
Mature 58.2% 62.8%