There has been a few views & nobody wants to reply? Well this is how I look at selecting a sire or dam.
I try to keep only P1 animals, that is animals which will breed true & every animal in the herd will express the same phenotype. If I open the herd it takes at least five generations to get back to a P1 foundation. When we outcross to a different phenotype we produce an F1 generation. When we cross the F1 generation we have F2, cross the F2 we get F3 & so on. If we back cross an F1 animal back to an original P1 animal we have an F1b, if we back cross an F2 animal to a P1 we will have a F2b, with a lot of the lack of predictability that is typical of any F2 animal.
Lets say I want to open my line & bring in another phenotype, maybe I'm looking at using a small bodied deer with big antlers over my big bodied deer with relatively small antlers. The resulting F1 generation will usually be magnificent, genetics is kind to us on this first cross because the results are usually very predictable & the way hybrid vigour works is that the best traits are usually the most dominant. These F1's are magnificent looking animals, but if you don't know what to expect from the next generation, stop here. I am happy to produce these F1's from P1 crosses but its very rare that I would breed them. They are always dissapointing as sires & dams & generally the best that the resulting F2 crosses from them can do is come within 75% of best traits of the original P1 animals.
If you understand there is a pattern in all the randomness of genetics, producing F2 animals can't be all bad. If they are used to produce an F3 generation the genes may just line up in a way that you produce a super star (consider this like a lottery win, someone has to win but the odds are poor). This generation can be very exciting if you have good animals turn up & the determination & patience to carry through to your objectives. Here we take the best F3 animals & produce an F4 generation. This F4 generation well start to have some predictability in its heritability, they will start to look like the F3 animals you selected to breed them from. Breeding the best of them will produce F5 & these will be very predictable in what they pass down. IMO I still think you need a couple more generations before you can consider you have established a true breeding line or have P1 animals again.
So what would I do if I was entering the whitetail breeding game? I'd go & buy the best P1 does I could find, that is all the does from the same place & with no out crosses for hopefully 5 generations. I would try to improve this line by selective breeding within the line but never introduce a different P1 F1, F2, etc animal to polute them. I'd need predictable P1 does to produce magnificent F1 animals using whatever good P1 bucks I can find by outcrossing for hybrid vigour. The resulting F1 animals would all be "terminal". I would never breed them (unless I wanted to start at least five generations of work), yes all the F1 does would be culled, every single one. Once I have the "recipe" for F1 animals they are 99% predictable every time. To do this I need to maintan (& slowly improve) my "foundation" herd of original P1 does as a seperate herd, including the best bucks from this line as sires. These are the basis of the recipes, which could include "typical" & "non typical" sires. Magnificent F1 bucks with hybrid vivour could be produced to order with 99% predictability, & again these would never be used as sires.
Has anyone ever bought a magnificent buck only to be dissapointed with its "pass down"? Have you ever considered if it was an F1 animal?