My herd is a commercial hodgepodge right now (Hereford, Red Angus, Charolais, Hillbilly Hybrid etc. etc), but I plan on acquring some more purebred Herefords over the next several months. I'm going to linebreed everthing around Keynote 20X, as there are so many different good indivduals down from him to use, without genetically painting one's self into a corner. A gradual effort to raise the Wright's Inbreeding Coefficient, or the Coefficient of Inbreeding over time; while being very selective in regard to brood stock, is a much better approach than quick hardcore inbreedings.
RWT hit the nail on the head about traits; both good and bad being exxagerated, and I think I stated somewhere else here once that linebreeding and inbreeding will give you 'Double the goodness and triple the trash". You've got to cull out anything that is undesireable, as it will become much more pronounced when line bred.
Without getting into a science lesson and boring myself and everyone else here, let us consider the benefits of inbreeding. A quick read of the text below will keep it simple enough to see the benefits.
Inbreeding Coefficients
While most breeders recognize that a mating between half-siblings or cousins represents inbreeding, the majority probably have no idea which represents the closer inbreeding.
The standard definition of inbreeding is that it is any scheme which results in the sire and the dam having common ancestors. This common heritage is expressed by a parameter called the inbreeding coefficient, first proposed by Sewell Wright in 1922. Designated F by Wright (but more commonly IC or IBC by breeders), it can theoretically range from 0 to 100%, and indicates the probability that the two alleles for any gene are identical by descent. Though the primary consequence of inbreeding is to increase homozygosity, the IBC is not a direct measure of homozygosity because the two alleles may be the same for other reasons. Within a breed, some proportion of all the genes will be the homozygous because there was only one allele to start with. In that sense, the IBC may be regarded as indicating what proportion of the remainder have been made homozygous by inbreeding.
The inbreeding coefficient is a function of the number and location of the common ancestors in a pedigree. It is not a function, except indirectly, of the inbreeding of the parents. Thus, one can mate two highly inbred individuals who share little common ancestry and produce kids with a very low IBC. (Because the potential number of ancestors doubles every generation, eventually you reach a point where the number of ancestors exceeds the number of individuals alive at that time. You are, therefore, bound to find some common ancestors if you go back far enough.) Conversely, it is possible to mate two closely related individuals, both of which have low IBCs, and boost the IBC substantially.
The % of IBC or WIC is simply this, a chance that the offspring will inherit traits directly from their parents rather than from either parent's background. Most stock within a breed today probably represent a pretty low IC around 1-5%, meaning there is only a 1-5% chance that traits will be inherited directly from the parents. Inheriting traits from the parents is what we want isn't it?! We breed to a great bull to get another him, not to get his great great great grandsire.
Well bred fault free individuals is the way will we more rapidly improve our genetics and consistently "lock in" the good traits of an exceptional individual or the traits of an entire breeding program.
