thinking about meat mutt weights

Just cut toenails and weighed our adults prior to breeding after a break. Was surprised to find that the doe that will be 2 years old next week was up to 8 pounds--she'd been between 7 and 7.5 for the past year and she doesn't seem overweight now. Our other doe is a full sister but a couple months younger. She's been just over 9 pounds for the past year. They both consistently have litters of 7 to 9 kits and are pretty evenly matched on the grow-oout time for the kits. The buck is just a year old and just hit 8 pounds. So I think those are small for adult meat rabbits (all mutts, NZWxSF) and wonder if I should be keep new breeding stock out of the heavier doe, since otherwise their performance is equal.
I don't feel very clear about when rabbits would be expected to stop growing. We're not feeding pellets or alfalfa so have slower growth than others report. I notice that when anyone asks about time to butcher the advice often is that growth slows significantly after 8 to 10 weeks so that any weight gain after that takes more feed than it's worth. But I've been keeping better records each year and our kits average a little over 2.5 pounds at 8 weeks and 4.5 at 12 weeks. I also read a lot about protein % in feed, but with our forage, hay & grain and/or roots diet, it often seems that calories are at least as important as protein. I think this because they do well in the fall when they get more roots and less grain, even though the roots are quite low in protein compared to the wheat or oats.
That was sort of meandering. My questions are 1) Should we be keeping youngsters to breed from the heavier doe? 2) Would you expect the growth curve to peak later on the diet we feed? 3) Is there something I'm missing about the importance of protein--or is forage we gather high enough in protein to make up for the low protein roots?

I think, honestly, and the importance of carbohydrate energy is greatly overlooked in conventional rabbit literature, but not by rabbit feed companies.

Although I see no mention of carbs on feed bags, there tends to be plenty of carb boosting ingredients in rabbit pellets.

I feel, it's probably an important piece to the puzzle as to of why rabbits tend to grow faster on pellets than on forage, even when protein levels are matched.

I fed my rabbits in a similar fashion to how you feed yours, Rainey, with the exception of hay type. I was able to get a good alfalfa hay (about 80% alfalfa) so protein was not such a concern here. Even so, I'll take a stab at answering your questions.
1) I'd grow the most promising individuals from both does and see how they are at 4-5 months. You can always thin the ranks then and use the culls as roasters rather than fryers.
2) Yes, I found that the growth of fryers peaked later when I quit feeding pellets. Since the natural diet was so cheap, I was never concerned about them taking longer to reach butchering size. I usually processed them at 14-16 weeks. My cost per pound was about $0.75 on natural feed; whereas on mainly pellets it was about $1.50.
3) Since your rabbits grow better when being fed roots as part of their diet instead of grain, I'd have to conclude that they are getting enough protein. (Unless, that is, there is a lot of fat when you butcher, in which case you might want to do some more thinking.)

There's usually some fat around the kidneys but not much anywhere else so I thought that was normal/acceptable. The meat overall is so lean--especially compared to pork which is the other meat we raise.
We'll be looking at a litter from each doe next month when they are 12 weeks, trying to choose a doe or two to breed next year. Think we'll keep this buck for another season unless there is one that is exceptional in one of the litters. We're pleased with how these 2 does have performed but don't know when they'll need to be replaced. They're only being bred 3 or 4 times a year and so far the litters are improving, not declining, but many people seem to think rabbits are getting old at 2 or 3 years. Making these choices about who to keep and breed and for how long is what I feel least confident about at this point. Guess it will seem easier as we gain experience. Still not certain how many does we want to be breeding, how many litters we want each year. This year we hadn't run out of rabbit from the late fall/early winter batches in the freezer when the first litter of this year was ready for freezer camp.
Thanks again, Maggie, for your patience with those of us just getting started and trying to figure things out.

I wouldn't

the final adult weight does not matter, unless you show and must reach a specific intermediate and/or senior weight

keep the meatiest and fastest growing kits and if they are only 8 pounds as adults all the better as you'll have
- more room in the cage
- generally they'll eat and drink less
- smaller poops that don't not get stuck in the flooring :x

My meat mutts rarely get over 9 pounds and a couple does are just over 7 :mrgreen: but their kits are all close to 5 lb at 10 weeks and the mothers can still easily feed a litter of 8

We start by not keeping to breed any kit that has had any health problem (like the one litter this spring where a couple had nest box eye). Then we look at the kits that are the biggest in their litter and sex them at 12 weeks. Any that have ambiguous looking genitals go to freezer camp. And some, like the buck we kept from last year, just are obviously not only larger but "meatier" than their litter mates. Not so confident though at judging overall conformation although I've read the threads on here and looked at the photos. Can recognize long neck or pinched hips in the photos of adults. How soon are such problems observable in still growing rabbits? At what age would you consider them old enough to judge between possible breeders?
I really appreciate folks helping me out with my questions in this next step beyond beginning with rabbits