Feb 14, 2014

Fryer Growth

I see a lot of people asking whether their weights for X-aged kits is "good" or not.  There can be quite a bit of variation in what constitutes "good," depending on what they're being fed, what breed they are, and how good the lines are.  There is actually quite a bit of research out there which documents weights of various meat breeds through various ages, and many which also compare different methods of feeding and/or care.  One of these days, I may put together a list of those papers, but for today, I'll just go through my own data.

Graph of rabbit growth rates.
Green line - crossbred average
Green field - crossbred range
Purple line - Rex average
Purple field - Rex range
Red line - Californian weights
Blue line - New Zealand average
I compiled data from 15 litters (9 undetermined crossbred, 3 Rex, 2 New Zealand white, and 1 Californian) from 3 to 8 weeks old (the crossbreds were only weighed at the 3- and 8-week marks; the purebreds were weighed weekly).  Litter sizes ranged from 2 to 9 (non-DOA), averaging 6.33 kits per litter.  All litters were fed on a diet of 18% crude protein pellets, plus occasional time on grass and infrequent garden treats.

3-week weights ranged from 9.8 oz. to 21 oz. (1 lb. 5 oz), averaging 13.2 oz.  8-week weights ranged from 43 oz. (2 lbs. 11 oz.) to 70 oz. (4 lbs. 6 oz.), averaging 54.1 oz (3 lbs. 6.1 oz.).

I'll admit that these are not ideal weights (the ideal goal would be 5 lbs by 8 weeks), but they still produce sizable-enough fryers to butcher at 10 to 12 weeks old, especially since at the 8- to 10-week-old range, fryers typically put on about 1/2 a pound a week (which would put the 10-week average at almost 4-1/2 pounds, and the 12-week average at nearly 5-1/2 lbs).  With that gain, they are right on target for the typical backyard breeder's goal of 5 lbs between 10 and 12 weeks old.

The big point of interest that I'd like to point out is how the litter weights cross around the 7-week mark.  I didn't post a graph of the individual litter weights, but there are also crossovers between several litters at 4 and 6 weeks, as well.  That goes to show that weights before 7 weeks are not reliably indicative of weights at 8 weeks or more.

Comparing litter sizes:
Litter size (number of litters)
2 (2)356 (2)7 (3)8 (4)9 (2)
3-wk wt.16.421.016.813.510.811.810.5
8-wk wt.55.670.068.050.849.552.053.1
From that data, litter size plays a marginally significant role in litter weights.

I also thought you might want to look at the data which shows how parents' weights affect the weight of the litters:

As you might be able to see from the data, the parents' adult weights really don't play a role in the growing weights of the kits.

I promise I will collect more data from upcoming litters, and probably make a new post showing weights through 10 or 12 weeks old.  I may also put together a chart showing the breakdown by litter size.