[Jacob-list] Linebreeding

[Neal and Louise Grose]

Mary and all,
I wrote the first part of this before I drank coffee this morning and the rest after others came in on the topic. I am going to have to come see those guys soon....maybe on the way back from hauling culls off to market!

Linebreeding is inbreeding done by someone who thinks they are a professional. I have also heard it said that linebreeding is inbreeding that works.

We practice considerable inbreeding here. I have yet to see any significant inbreeding repression. There may well be a good reason for this. In the poultry industry, perfect all-the-same chickens are the result of crossing strongly inbred SIB lines. These inbred lines are created by intensive inbreeding of generations of siblings. [This is a much better way to handle "linebreeding" than crossing of parent back to offspring...i.e., use the old bugger 'til he croaks.] In poultry, defective chicks don't hatch. This is very effective at eliminating adverse defective genes before they become established in the gene pool. Something very similar to this may have happened in Jacob sheep. The history of Jacob sheep is one of isolation of breeding groups and inbreeding. When a minimum amount of care is given to these animals, and heavy culling is practiced, weak sheep are effectively eliminated from the group. The resulting gene lines are more narrow, but stronger. This is only a good idea only up to a point, but may be the reason we see relatively few genetic deformities in Jacob sheep. 

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