I am also wondering if they don't like the Modesto I'm transitioning to.
Ah-ha! This might be the problem, in which case I would have fewer concerns about using the doe as foundation stock. If your doe started failing sometime around the feed switch, that could easily be the issue. Some rabbits seem able to move among different feeds seamlessly, while others can really struggle, but in general, a rabbit's gut biome needs time to catch up and re-balance in response to feed changes. This, of course, can be related to genetics (like all tendencies) but is not high on my list as an important selection criteria since it does not seem to be related to overall gut resiliency (for example, tendency to weaning enteritis), at least in my barn.
How much oats and BOSS can I feed daily? Maybe I am not feeding enough? It's a couple of heaping tablespoons of each 2x a day.
At this point, I'd give her as much as she wants, of anything she will eat. She's apparently off-kilter in her gut, and allowing the rabbit to make its own choices, to balance its gut itself, has worked for me in the past. That's why I'd offer her lots of different options. If she's wanting more of the oats and BOSS and less of the pellets, she may be allowing her gut to slowly acclimate to the new pellets. Oats and BOSS can make rabbits fat (not a concern right now with this rabbit!), but even though they love the treats, my rabbits do have a limit to how much they will eat and if it's exceeded, there will be grain and seeds left in the treat dish. Your goal may be to get her on the pellets as her main ration, and if they're good pellets, eventually she shouldn't need a lot of supplementation, but it might take a while to get there.
I gave a dab of Safeguard to the two crosses that came in with ear mites last September, even though I don't see any active right now, because they did have a relapse and I treated more liberally the second time with coconut oil.
I don't generally use the Safeguard for mites; it may very well work, but I've relied on oil (olive, sweet or even mineral oil) for ear mites, and ivermectin for particularly persistent fur mites. If you're having recurrences, it would be worth trying to figure out where they're coming from: solid wood in the hutches, straw, hay, other animals?
Susceptibility to suffer from parasitic infestations can also be a genetic predisposition, whether it's directly related to the body's response to the parasite, or an overall tendency to be less robustly healthy. I've found that rabbits that are stressed are far more likely to suffer problematic mite infestations (and all other ailments, actually). If I have a rabbit that gets repeated infestations in my barn - those that are not a result of living at the fair for weeks - I tend to cull, since it indicates a tendency not only to infestation but also to higher stress levels. Less stressed = more health; easily-stressed or high-strung = more health problems.
The AB kits are actually bigger than my New Zealands and are a half day younger and weren't fed the first two days, or only got colostrum. I'll see what they look like in a other few weeks.
Kits not being fed for the first few days could be another red flag regarding the doe, but I'm guessing it was her first litter and maybe she'll get a pass for that. Although, most of my Satins are good right out of the gate, so that's something else to select for when you actually have options from which to select!
They are lighter than the slate blue they should be. My new buck seems better quality but he's got weird ears. My doe came from a colony.
I would dearly love to cross in a Beveren, also rare, sigh.
All of these observations change my first suggestion for an outcross to Flemish. Beverens have a very pale, almost lilac blue color, so that would not help your line, while Flemish blue is a similar shade to American blue. Beverens have a distinct breed-characteristic v-shaped ear carriage, while Americans and Flemish both call for upright ear carriage. And Flemish are a lot more common, in most areas anyway.
Finding a smallish Flemish probably won't be all that difficult, and they will be the ones that breeders want to offload, if they're not culled right away. I'd try to find a Flemish breeder with blues and let them know what you're trying to do. If you're moving away from an extreme (Flemish size and bone, in this case), that's a lot easier to do that than recovering an extreme quality, so it would probably not be super challenging to select for crossbred offsping with bone and size appropriate to Americans rather than Flemish.
By the same token, NZ could offer a decent cross, especially since you already have them. The NZ standard also calls for a deep, rich color and upright ear carriage. Their body type is of course different, but in my experience a long shoulder is a lot easier to
get than to
eliminate (again, that extreme compact/commercial body is only maintained by heavy selection)! And if your NZs have good depth, that might really benefit your Americans, which although they have a longer, lower shoulder, are still supposed to have good meat-producing depth in the hindquarters.