OK...I have talked to a few friends here on BYC who have discussed Line Breeding with me. For those of you considering it..it can be a bit confusing but I thought I would post some info for those who are working on projects or just trying to improve their line.
Line Breeding is when you breed chickens in the same family. First..you never breed mother to son, father to daughter or siblings from the same parents, aunts and uncles to cousins. This is Inbreeding and there are issues that can cause a lot of problems down the line in that groups gene pool or even from the immediate chicks from this breeding such as sterility, bad toes, combs..and son on.. Now,,you can breed within your flock but you have to be careful how you do it. Why people Line Breed is to keep the coloration more defined as well as confirmations..combs..etc. If you do that here is how you would go about it.
Your first generation (F1) parents breed and produce your F2 line. You will take new blood which will have a different gene pool and breed to your F2 generation. Then...to line breed you take your F3 generation and breed back to your original F1 generation. You are still copying your original gene pool but you have another gene pool added from the new blood you bred into your F2 generation to offset your duplication. What you want to make sure is that you have 2 generations separating what you breed. But it is ONLY the grandparents or their siblings from that generation that you breed your F3s to. I hope I am not confusing you. Believe me...chicken genetics are very confusing. I have a couple of webpages that simplify breeding results for coloration, pattern...etc. I will find them and post.
If you are breeding new colors like lavenders, porcelain ...newer developed colors..Line Breeding helps keep them from becoming diluted in color as well as loss in things like leg length..tail set..etc.
If you are working on a project you have to keep in mind what is in your gene pool from your original start. To effectively develop a certain look you want takes a minimum 5 years for it to start breeding "true". For instantance.. if your project was to develop a lemon cuckoo ameracuana you know for certain that when the eggs hatch they are going to be like the parents. Now...keep in mind that there is always a possibility down the road that something different or odd can pop up. Sometimes some of the other genetic traits from stock that you used during your early development can come through in earlier chicks after 5 or 6 generations. For example.. my mare, by all genetic rules and standards, should only throw buckskin with my stud...yet this past summer she threw a blue roan which had not appeared since 5 generations back in her lineage. That one gene was there but was only a minute amount. That is why most breeders do not consider their project birds viable until after F8 breedings.
When you are buying eggs or chickens that are a fairly new coloration, pattern. etc..always ask what generation the eggs or chicks you are buying comes from. If the person selling them does not know they probably bought theirs from the person who developed it or someone down the line during development. What it boils down to is..when it comes to new variations of breeds always keep in mind you may get a surprise depending on how defined the genetic pool is. When I bought the eggs for my Crele Polish...the seller never disclosed to buyers that they where still in project stage and my F2s developed into 3 different colorations. so...I will have to work at least 4 more years to be comfortable in saying mine are completed. Info like that could have helped me when I started these if the people had been honest instead of greedy.
So...I hope this helps some of you who are working on developing or enhancing your bloodlines and those who are trying out new types of a set breed.