Originally Posted by 3riverschick Hi, Wow, what a thread! I think there are 4 things going on here in his thread. 1st and 2nd are different schools of thought needed to breed mammals and poultry. Tho both fields are husbandry, the rules for each are only generally similar. The specific sub-rules needed for success are different in each case. The sub-rules of breeding for success in mammals do not translate into the poultry world because of poultry's wider genetic base and plethora of sex-linked genes. 3rd and 4th is the subtle , but complete, dichotomy between classic animal breeding and the "biodiversity movement". Let's look at 1 and 2 first and how they affect 3 and 4. In the mammal world, there tend not to be as many sex-linked genes. In Mammals, the laws of inheritance produce creatures which appear with closer genetic rigidity to the forms of their parents. Because of this, the rules for maintaining genetic diversity are more closely adhered to. We see stronger admonitions to "breed 3 generations in, then out-cross"., etc. And other genetic rules based in science or tradition which help prevent " inbreeding depression" in the mammal world. We see strong admonitions to always be wary to maintain genetic diversity to a point which constantly avoids inbreeding depressions' effects. Yet, because the laws of inheritance produce creatures which appear with closer genetic rigidity to the forms of their parents, we also see counsel to found strains from disparate sources so we have the genetic "maneuvering room" to select for the particular traits/type we wish to see in our new strain before the laws of inheritance restrict our biodiversity to the point we need to out-cross. The lack of a plethora of sex-linked genes makes this necessary. Enter, the poultry world. Where sex-linked genes are king and color is an integral part of breed type. Because sex-linked genes exist not only in structural phenotype, but in the plumage as well, we see a creature which has much more aptitude for genetic variation than the mammal. Now the rules have changed. At least the sub-rules have changed. Variation is not longer sought as a friend in building type by setting type. Variation in poultry is managed as a detriment to proper breed type. Necessary and a threat at the same time. This is why we see counsel from veteran breeders to start out with birds from a vintage line-bred strain and work within that strain to create the bird which both adheres to the SOP and delights the singular vision of that breeder's artists' eye. Unlike the mammal breeder, we are counseled not to strain-cross to found flocks because of the exponential increase in genetic variation which results. Sufficient unto the strain is the variation therein. If more variation is ever needed, strain-crossing should be done to a closely related stock of the same breed which was founded in the same gene pool as the flock needing the strain-cross. ( No, I am not addressing the rare case where a breed is in such critical need that a cross-breeding to another breed is needed. That situation is so rare, that it is not a viable argument on which to build general counsel. It is an aberration needing wisdom and guidance from veteran breeders. ) Ok so how do our 3d and 4th aspects of this discussion effect outcome in our breeding programs? For decades now, there has been a movement advocating biodiversity, based mainly (in my opinion) on a fear humans are impacting the lifeforms on this world faster than their natural ability to evolve and adapt to these changes( however the biodiversity advocates tend to describe "the changes"). The idea is that we should found our groups of breeding animals on as wide a genetic base as possible and keep in-breeding to minimum so the creatures will be as robust, healthy, and able to work as possible. All selection is done with robust health and ability to work as the premier goals. Breed type is unimportant except as regards the general appearance of the breed. Specific "points" of the breed are ignored , except as they are needed to produce robust health and ability to work. The creatures do meet the general phenotypes for their breed. To the classic animal breeder, this is a beguiling movement. Especially if the breeder is engaged in wanting to preserve a threatened breed. Let's take a closer look at how biodiversity and classic animal breeding don't mix. Don't and never will. They are like oil and water to each other. On the surface they appear to work well together when one shakes the general ideas together. But in practice they stand apart from each other. Each of their central counsels so fundamentally different that the two cannot long coexist in a breeding program (especially in the poultry world). Why? What are "biodiversity advocates breeding? They are breeding "Land-races". Groups of animals allied by general breed type only , robustness and ability to work, but not (this is all important) by specific points of the breed ( such as color). What are classic animal breeders breeding? "Specialized animals" defined by the specialized points of their breeds for a specific purpose which includes selecting for health and utility. If one approaches a biodiversity advocate about incorporating their ideas into a classic animal breeding program, it will not be long before the two parties come to an unconquerable divide over the need for special points in a breed. In the case of the classic animal breeder, these points of the breed are inexorably linked to the proper functioning of the creature (esp. in poultry). To the biodiversity advocate, these specialized points of the breed are an impediment to the successful creation of the creature because they are not strictly allied with health and ability to perform. Ok, so how do we put all these ideas back together again in this conversation? Yes, we must have genetic diversity for genetic progress. That statement has merit on its face. However, it stops being true when we move from classic animal breeding into the realm of the biodiversity movement because they and we have different goals. We cannot mix the two fields of thought and expect success. Again, it is mentioned that out-crossing or cross-breeding is a viable option when diversity is needed. Yet we see in poultry, (as opposed to mammals) a wider genetic base and the plethora of sex-linked genes allows us to choose either a back-cross in our own strain or a loosely aligned relative who was line-bred from the same gene pool as our stock. In poultry, this could even be a bird from the same strain as ours, raised for over 7 years and at least 500 miles away. In conclusion, we can make all kinds of statements about breeding programs, essentials of genetics, and biodiversity. Yes, we must never forget our basic parameters for breeding are classic animal breeding in the poultry world. When we begin to add in counsels from other realms and philosophies, we shift our basic parameters so they are out of sync with our goals and techniques. That bodes a sincere threat to our success. Best Success, Karen Tewart So this imporatant topic can be sanely debated off the heritage breed thread, I have taken it upon myself to start the thread with this impeccable psot by Karen. Thanks Karen.