For me.....
I do things "the old way"... and my expectations are low compared to the "modern" rabbit breeding people.
I fed a high calorie, high fat diet ,that was/is "relatively" low in protein..
I had breeding problems, with does getting internal fat ,only if my breeding schedule was interrupted/ paused .
As long as my does were rebred at 5 weeks after kindling, I had no breeding problems from internal fat.
My weaning averages were above 8 , so the calories the does ingested went to milk production.
The fryers, did have some extra internal fat... I think it is yummy, especially in gravy...... and... it is great for making lotion, salve, and boot dressing.
-- beginning many Years ago, I fed root crops, mostly sugar beet, J. artichoke, mangles, and carrots,... all high in fat producing calories. I fed a huge amount of kale, weeds, and chicory greens. I always had grass hay, or corn stalks in the manger. I also fed "sheep minerals"..
In my estimation... I had great production.
These are new times, rabbits have become pets, pellets have become the "standard" feed. The rabbits we get now will have been raised for many generations on pellets. The production expectations are much greater than my 5 week rebreeding schedule.. The expected growth rate, is much more than my 4 lbs at the 8 week weaning , goal.
Feeding my way..I had a lot of young rabbits that were weaned into grow out cages, awaiting the 4 lb butcher weight..
When I get a new batch of breed stock nowadays.., I always have to "gradually" breed for rabbits that can excel being fed "my way" -- it takes a few generations.