[Jacob-list] inbreeding/linebreeding

[Thomas Simmons]

As a general rule, using as many different rams as possible within a flock provides the greatest genetic pool and the smallest chances for negative recessive traits to become established within a flock.  Let us understand that *most* Jacob breeders are small holders, and do not have the luxury of keeping many rams, and inbreeding can become a problem.  However, if you are able to keep several "lines," that doesn't mean you necessarily want to just breedacross lines, either; you may prefer line-crossed ewes, but line-bred rams.  This is not the same as inbreeding, and, done properly, does not have to be problematic (Inbreeding is *not* bad in and of itself; it can bring out the best *and* the worst in a line.)

Use of the same ram, every year, on the same ewes and their offspring, may lead to the inbreeding difficulties mentioned by Mary in her last post.  The difference between line breeding and inbreeding is truly the degree of relationship between the ram and the ewe, as well as the overall "picture" of what is happening inthe flock.   Sire to daughter and brother to sister result in the highest "inbreeding," and should be avoided if possible (Math folks may wish to play with Inbreeding Coefficients, which measure the amount of genetic material that is being duplicated in the progeny of the breeding pair)   

Example: I have bred a Waldo Line ram (my own terminology here!) to a Killorglin line ewe.  If I really like what i see in the Killorglin line, I may then choose to breed the resulting ram progeny to another Killorglin ewe (maybe even an aunt) to produce another Ram with an even higher "Killorglin line" genetic base.  The purpose of this would be to capture a particular line's traits in a ram. Then, i would use this ram on ewes from other lines, thus imparting the best of the Killorglin line over ewes from other backgrounds, thus hoping to minimize recessive problems AND add overall vigor the next generation's stock.

thom



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