When breeding..

[Maeschak]

Fastest maturing birds can be determined as early as 6 weeks of age. 12-14 weeks of age is great time to butcher. As mentioned hands on breast and body evaluation is a must.

Here's a good article on evaluation of meat birds:

https://livestockconservancy.org/images/uploads/docs/ALBCchicken_assessment-1.pdf

I just used this evaluation tool a few weeks ago when culling a few cockerels (looking for the best one) and it was great. I was so focused, however, on getting the right 'feel' of the body (girth sizes, angles, etc) according to the tool, that I completely forgot to check over the easier stuff... I had chosen my best keeper cockerel and the next day I realized he was cross-beaked! I had never seen it before on him and it wasnt a bad cross-beak but certainly not a cockerel worth breeding. I really have no clue how it happened as I hatched all the cockerels and have never noticed the cross beak (and I do a lot of staring when they are tiny). So perhaps it was some sort of injury later in life- anyway, the point is don't forget the obvious stuff!

 

[Egghead_Jr]

That sort of thing happens to me all the time. You get so focused on "insert characteristic here" you miss others. Last year for me it was leg color I missed.

Big breeders will put birds in individual cages for days on end so they can walk up and down the row of cages taking notes on each bird to ensure they didn't miss anything.

 

[Ridgerunner]

I just used this evaluation tool a few weeks ago when culling a few cockerels (looking for the best one) and it was great. I was so focused, however, on getting the right 'feel' of the body (girth sizes, angles, etc) according to the tool, that I completely forgot to check over the easier stuff... I had chosen my best keeper cockerel and the next day I realized he was cross-beaked! I had never seen it before on him and it wasnt a bad cross-beak but certainly not a cockerel worth breeding. I really have no clue how it happened as I hatched all the cockerels and have never noticed the cross beak (and I do a lot of staring when they are tiny). So perhaps it was some sort of injury later in life- anyway, the point is don't forget the obvious stuff!

Sounds like something I would do.

 

[MBK Farm]

Here's a good article on evaluation of meat birds:

https://livestockconservancy.org/images/uploads/docs/ALBCchicken_assessment-1.pdf

This is a great resource to get you started +1
Then the book, Call of the Hen, which can be found free on the Internet is further reading with more specifics regarding type to look for when selectively breeding. This method also served as the underlying evaluation guide for the ALBC Buckeye restoration project.

Lastly, your best breeding tool is a well made, sharp hatchet. Dr. Hatchet is very good at what he does. He fixes all the problems, 100% cure rate.

Good luck and be prepared for the time commitment (2-3 seasons at minimum, but most likely 3-5 depending upon your starting point).