Breeding Matters 111 - Inbreeding vs. Line Breeding
Jan 27, 2015 19:25:21 GMT -5
midhilldexters, legendrockranch, and 2 more like this
Post by Cascade Meadows Farm - Kirk on Jan 27, 2015 19:25:21 GMT -5
For a production herd, it's great to cross one inbred line on another inbred line and that can give you maximum production results from heterosis in the first generation, but that can become a murky mess in subsequent generations and you lose your heterosis gains if you're not careful in those subsequent generations.
We've had a closed Icelandic sheep herd, and closed Dexter herd, and closed chicken flock (2 breeds), and closed American Guinea Hog herd for over a decade. Having a closed farm is allowing us to tune our genetics. I think of it as a big puzzle.... if you keep working on jigsaw puzzle you'll eventually reach your goal... but if you keep repeatedly bringing in another big box of puzzle pieces and dump them in the pile, it can greatly complicate things for you.
In the case of genetics, the puzzle pieces are alleles... You might possibly have all the alleles (gene versions) you need with as few as a handful of starting animals, or you might need a dozen or so animals to provide you with the all alleles you need. You'll figure it out along the way.
Planned inbreeding is ALWAYS successful because inbreeding either works, or if doesn't work, then it gives you very valuable information. Inbreeding doesn't create any problems, it just allows existing problem genes to pair up and exhibit themselves which is useful for elimination of those genes.
Inbreeding makes animals homozygous for their genes / traits... That's VERY good if the animal has amazing traits, but can be problematic with any weak genes/traits because you will lock those weak traits in place permanently if you're not careful.
While being homozygous for all their amazing traits is very good, the immune system works better if there is some heterozygous variation there. When selecting animals, you'll want to remember to cull any that have weak immune systems or weak ability to fight parasites or weak reproductive capability. This can mean that you shouldn't be too quick to use de-wormer (so you can see your animals that have a natural weakness to parasites)... and you shouldn't be quick to call vets or to fix sick animals (so you can test their immune systems). That's easier to do in larger herds where you can afford some losses.
While we have a closed farm, we are willing to bring in outside animals if we are lacking any important alleles in our existing herds/flocks. This year, for the first time in over a decade, we're considering bringing in some outside American Guinea Hog genes to give us 14 teats instead of 12 which seems to be the current maximum in our herd. But bringing in these outside genes could mess up a lot of other things for us so we'll have to be VERY careful.
Once you get a linebreeding/closed herd program going and you make good progress in tuning your genetics, you'll want to only go outside (very carefully) to address a specific issue.
By having LESS diversity on each of our farms, we actually create MORE diversity for the breed. If everyone tries to get maximum diversity on their own farm then we all end up with the same blended gene pool, but if more of us try to create our own lines, then instead of having one big blended homogenized national herd, we'll have a whole bunch of distinct lines, and we can dip into each others' distinct lines when a need arises.
PS. I believe all AI Bulls should be considered highly experimental until they breed at least 10-20 of their own daughters with results reported. A great bull should be able to be bred on many of his own daughters and get great results. This would also help uncover any hidden problem genes/lethal genes before those genes are spread far and wide.
We've had a closed Icelandic sheep herd, and closed Dexter herd, and closed chicken flock (2 breeds), and closed American Guinea Hog herd for over a decade. Having a closed farm is allowing us to tune our genetics. I think of it as a big puzzle.... if you keep working on jigsaw puzzle you'll eventually reach your goal... but if you keep repeatedly bringing in another big box of puzzle pieces and dump them in the pile, it can greatly complicate things for you.
In the case of genetics, the puzzle pieces are alleles... You might possibly have all the alleles (gene versions) you need with as few as a handful of starting animals, or you might need a dozen or so animals to provide you with the all alleles you need. You'll figure it out along the way.
Planned inbreeding is ALWAYS successful because inbreeding either works, or if doesn't work, then it gives you very valuable information. Inbreeding doesn't create any problems, it just allows existing problem genes to pair up and exhibit themselves which is useful for elimination of those genes.
Inbreeding makes animals homozygous for their genes / traits... That's VERY good if the animal has amazing traits, but can be problematic with any weak genes/traits because you will lock those weak traits in place permanently if you're not careful.
While being homozygous for all their amazing traits is very good, the immune system works better if there is some heterozygous variation there. When selecting animals, you'll want to remember to cull any that have weak immune systems or weak ability to fight parasites or weak reproductive capability. This can mean that you shouldn't be too quick to use de-wormer (so you can see your animals that have a natural weakness to parasites)... and you shouldn't be quick to call vets or to fix sick animals (so you can test their immune systems). That's easier to do in larger herds where you can afford some losses.
While we have a closed farm, we are willing to bring in outside animals if we are lacking any important alleles in our existing herds/flocks. This year, for the first time in over a decade, we're considering bringing in some outside American Guinea Hog genes to give us 14 teats instead of 12 which seems to be the current maximum in our herd. But bringing in these outside genes could mess up a lot of other things for us so we'll have to be VERY careful.
Once you get a linebreeding/closed herd program going and you make good progress in tuning your genetics, you'll want to only go outside (very carefully) to address a specific issue.
By having LESS diversity on each of our farms, we actually create MORE diversity for the breed. If everyone tries to get maximum diversity on their own farm then we all end up with the same blended gene pool, but if more of us try to create our own lines, then instead of having one big blended homogenized national herd, we'll have a whole bunch of distinct lines, and we can dip into each others' distinct lines when a need arises.
PS. I believe all AI Bulls should be considered highly experimental until they breed at least 10-20 of their own daughters with results reported. A great bull should be able to be bred on many of his own daughters and get great results. This would also help uncover any hidden problem genes/lethal genes before those genes are spread far and wide.