You will have to look at the calorific value of the feed your are giving the rabbits.
This is a rough guideline of producing meat rabbits on a commercially produced pelleted food.
Which sadly does have a massive variation for nutrition , vitamin & trace elements for every batch produced by the mill.
It's to do with the natural variations in the crop growth season the harvesting method employed & sometimes stored quality of the finished basic elements such as paper sacks or plastic sacks , bulk blown into a feed silo quantities , weather at the storage and age of the basic ingredients plus the types of binding oils used.
There are charts detailing how a commercial breed such as a Carolina meat or a NZ meat or a cross of them run /grow develop . These charts are often titled feed conversion rates ( FCR ) taking the above paragraph into account even these specialist charts can vary tremendously .
I'd look for the charts nowadays in some of the American Agricultural college extensions .
Whatever conclusions you draw from any of these charts remember that most of the charts will have been promogulated from data obtained in nigh on laboratory conditions. So if you calculate everything out to the Nth degree , like as not you'll be much nearer the mark if you divide the final cost by two .
When I did our calculations & presented the sources of info & my figures for a 1 , 2, 3 & 5 yr. business plan to the enterprise board & my bank they were both straining at the leash to give me EU funding or have our account .
It proved over time to have been a rather over enthusiastic set of plans our end profits were less than half of the projections for various reasons most of which were out of our control.
Don't go & look at any sales blurb from any of the zillions rabbit equipment sellers or organisations no matter how long they have ben in existence that concerns rabbits & projections as these will tend to show you what is theoretically possible under perfect conditions . As we all know only too well you'll be darn lucky to actually attain half of their suggestions .
I can't give you the exact figures for I'm no longer in the business. how ever I seem to recall though cannot say for sure that at the outset in 1989 when I did the initial calculations feed was around £ 90 per tonne , for three tonne batches of 25 kg ( paper ) bags of pellets from a local feed mill
Here is a very , very rough guide
100 gram of feed per non pregnant doe or the buck per day , this is a maintenance diet
First few days of pregnancy this is upped to say 130 gram per day for the doe.
By the end of pregnancy term this goes up to almost double and carries on whilst she is suckling her kits.
The kits .
You need to see what they as a litter can handle by feeding them twice a day weigh what you give and what is left by the time you go to give the evening feed and dividing the amount by the number of kits. This gives you the base figure
Kits waste an awful lot of feed , about three times as much as a single doe or the buck . Often by peeing in the feeder or by scratting it out .
The amount of feed required increases , at first gradually ,then as they get to about five weeks old it starts to increase tremendously as they grow bigger & produce more heat and meat . By the age of 8 weeks old at the supposed harvesting time they will only give you just over break even costs . After 8 weeks old and up to 20 weeks old they will eat you out of house and home sometimes needing 400 gram or more per day of commercial pelleted feed .
Please do not be dazzled by the price of say £ 18 per Kg of prepared rabbit meat in the supermarkets / specialist shops , as their mark up is usually well over 6 times the base price they pay to the processor . The processor in turn marks up what he pays for the farmed rabbits by the same amount for he cannot survive on anything less.
Even my mates who are rifle and ferreting experts struggle to cover the cost of the ammo or fuel when selling fresh rabbits by the score , jacket on , pissed & paunched ( JOP&P'd ) to game dealers.
Frozen or a held JOP&P'd for a couple of days in a very cold chiller till they get a batch of hundred or so attract even less money .
One route that did prove profitable to me was locating individual customers or clubs with a high ethnic content from the former eastern states communities . Word of mouth was the best advertising here. Though nowadays these folk tend to be established & are doing their own direct sourcing legally or otherwise .