11/01/2022
Rabbits are seasonal breeders and they are designed to have multiple litters of kits in a single breeding season, as well as being able to have more litters in the less typical seasons if their health and the weather allows. Their hormonal and energy consumption pathways will be all fired up and switched over into baby rearing mode, and it can stay that way for the entire season.
As we've domesticated rabbits, and many people have bred them for specific traits, some lines may have been bred away from this ability to have litters back to back because their own muscle maintenance uses up more calories than the lighter frame of a wild rabbit. This is why we don't usually breed domestic rabbits immediately following kindling (birth), as many wild rabbits will.
It is still more beneficial to the doe to have several litters back to back before a longer rest, but that doesn't necessarily mean having a litter every 4 weeks.
Kits are typically weaned at 5 weeks of age, though some does will wean them at 4 weeks and some will allow them to continue nursing past 8 weeks.
That said, 'weaning' and 'separating from dam' are different times. They may be weaned by 5 weeks on average, but occasionally you get a kit that is late to eat solid food. That's why I try to separate them from their dam between 6 and 7 weeks. Then, by 8 weeks, they've been on solid food without access to nursing for at least a week and are safe to sell.
Once the kits are separated, it would be safe for her to have a second litter. So the general recommendation would be to rebreed about 2 weeks post-delivery. This gives her birth canal plenty of time to recover from delivery so mating isn't uncomfortable. Growing kits don't take up many of her calories, so she's still plenty capable of nursing her litter. And toward the end of gestation, she will be more likely to firmly wean her current kits as she prepares to take on a new litter before you need to separate them, reducing weaning enteritis.
Every rabbit is an individual, and some may require slightly longer breaks, or shorter breaks, than others. I have a netherland dwarf doe that starts mounting her own kits if she hasn't been re-bred by the time they're 4 weeks old, and some large breed does that are totally fine with having her 3 month old offspring still sharing her cage. Some does keep their weight better after litters; and which feed you're using can really influence this as well. Those feeding lower calorie and protein feeds may need to give their does longer breaks.