Thursday, March 14, 2013

RE: Cross Breeding Americans

*Somebody on the yahoogroup asked about Americans and hybrid vigor. My answer:

Okay, my opinion on cross breeding with Americans.

First of all, the Americans are a unique, heritage breed. Keeping the breed with clean blood lines is a priority. Keeping the breed with clean bloodlines also simplifies breeding programs.

Breeding Americans to Silver Fox for meat would be okay IF you don't have a breeding pair of the right breeds and you need the meat. More of a "necessity" than a best course strategy.

Cross breeding for hybrid vigor does not always work. Not all crosses create hybrid vigor. Sometimes the genetics of two certain rabbits will not be vigorous when crossed. Don't know why, but it just IS.

Crossing for meat usually you have similar bodies. American is mandolin body type. Most everything else, like Silver Fox, is commercial body type.

The goal of crossbreeding for hybrid vigor is to squeeze another 3 to 10 percent of growth for meat production.

To do this as an ongoing, sustainable practice year after year is a challenge. It means having to maintain separate blood lines of rabbits or two herds. Because one needs separate bloodlines to "cross" breed.

How many cages does that take? Each breed will need at least the usual 2 or 3 doe cages plus 1 or 2 buck cages, plus 3 or more growing out cages. So that is 8 cages for each breed, 16 cages more or less. If one has a lot of cage space it is not a problem.

If fast growing litters is important, than select for fast growing pure breed litters. Select the fastest growing, best body type to use for the next generation of breeding stock.

When breeding for fast growing litters, one should also be selecting for easy breeding, good mothering, number of kits raised to butchering. *Also consistency. All similar size in the litter, not 3 meat bricks and 5 mediums.

Focusing on one breed allows one to concentrate the cage space. Take that 16 cages from the above example. One could have litters going all the time, giving ample selection opportunities. ONe would also have cage space to grow the "keepers."

To freshen the genetics of the herd one could pick up a doe from an outside herd every two or three generations.

When a new buck is brought in the herdsman tends to breed it to a lot of does. A new buck's genetics may not interact well with the herd and now we have a whole generation to cull out.

Bringing in a doe gives a chance to see how it blends with the bucks. If it works one can keep a breeding buck from the litters. Now we have a buck with existing herd genes and additional genes from the outside doe.

If it doesn't work well than we only have to cull one doe and the litters.

There is another way to use crossing with Americans. Keep separate American White and Blue herds. The NZ breeders have been keeping colors separate for years because the strategy works. If one needs some hybrid vigor for meat production, than cross the colors.

Keeping separate color herds allows the maintenance of separate gene pools that can be mixed as needed without spoiling the pedigrees.

I think the push to blend Blue/White breeding so all you get is Blue/White litters is done at the risk of homogenizing the gene pool. An all Blue/White genetic herd will have a lot of wild cards eliminated. Wild card genes can be good or bad, but if we don't have them we will not be able to use them in the future.

So those are my thoughts on cross breeding Americans. Overall I think it is not necessary and counter-productive. We need rabbits that have the trait of fast growing litters without bringing in an outside buck. If we grow dependent on hybrid vigor to correct a deficiency in our herd then we have not fixed the problem.

That's my opinion. Your mileage may vary.
Void where taxed or prohibited.

Have a joyful day!
Franco Rios

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