SOP's Can you help, or do you want to learn?

[Amer]

How much is known of the genetics that influence bodytype? Like how the tail or wings are carried or how "full" a body looks?

Overall type is a quantitative trait. Quantitative means it is influenced by many unknown genes.
However, obvious faults and disqualifications like split wing, stubs, and crooked toes are often caused by simple recessive genes that can be a pain in the neck to eliminate.

 

[Sic]

Body type in poultry is considered a quantitative trait, which means it is influenced by multiple genes and is not controlled by a single gene pair. This type of inheritance is also known as polygenic inheritance. Traits such as body weight, body size, and shank length are examples of quantitative traits in poultry.

Quantitative traits are influenced by many genes that might interact with each other (gene × gene or gene × genotype interactions).

These traits typically have low to medium heritability, making it challenging to improve them through traditional direct phenotypic selection alone. IMO, this is why it is so much easier to start with a pair of birds that have the desired phenotype regardless of breed (purebred doesn't really exist in chickens)

 

[Amer]

Direct phenotypic selection is the only way to improve these traits though, difficult or not. And it is not impossible to get good birds from hatchery birds. I know someone who bred show quality d'Anvers from hatchery ones. Hatchery ones have a lot of genetic diversity. Many of them have all the necessary genes to get the correct breed type but they have a lot of other genes besides, and it is only by inbreeding birds with the desired traits that you can get show quality birds. Yes, I said it, the dreadful inbreeding word. Inbreeding is a tool, it can be used for good or evil, just like a knife. The trick is to inbreed the good traits and eliminate the bad ones. If faults emerge, they were already in the gene pool. It is the job of a responsible breeder to eliminate them, and to select for vitality always.

 

[Sic]

Direct phenotypic selection is the only way to improve these traits though, difficult or not. And it is not impossible to get good birds from hatchery birds. I know someone who bred show quality d'Anvers from hatchery ones. Hatchery ones have a lot of genetic diversity. Many of them have all the necessary genes to get the correct breed type but they have a lot of other genes besides, and it is only by inbreeding birds with the desired traits that you can get show quality birds. Yes, I said it, the dreadful inbreeding word. Inbreeding is a tool, it can be used for good or evil, just like a knife. The trick is to inbreed the good traits and eliminate the bad ones. If faults emerge, they were already in the gene pool. It is the job of a responsible breeder to eliminate them, and to select for vitality always.

I agree. I do know of breeders that have tried to influence body size in a breed by outcrossing to another breed, this can open up a whole new can of worms because they aren't just bringing body size and often ends in failure to improve your stock. Inbreeding is a very important tool, especially useful to unmask recessive genes.

 

[Sic]

I have purchased hatchery partridge chanteclers specifically for genetic diversity, half of them didn't remotely resemble chantecler except for a partridge pattern. In the end I have selected one cockerel and 3 pullets out of the 25 I received. Select the best - eat the rest is the way.