Modern swine have 19 pairs of chromosomes

Simple Gene Inheritance

Multiple Gene Inheritance

An example of multiple gene inheritance: Growth Rate

Growth rate depends upon

Each of these above activities/functions may be controlled by other sub-characteristics thus multiple gene pairs.

Thus to select for greater growth rate (or any other multiple gene trait), you must collectively select for improvement in all genes that code for functions and structures having an impact on that trait.

In some cases, improvement in one function is linked to a setback in another function, thus making overall progress in the desired trait difficult.

Effect of the Production Environment

It is often very difficult to separate genetic influences from environmental influences.

Heritability estimates are efforts to differentiate between those two forces.

Environmental influences are not transferred to offspring, thus heritibility is only the result of gene transfer.

Some Common Terms

Prepotency

Nicking

Pure Breeding

These are matings of animals derived from a common, distinctive ancestor

Breed Association or Registry

This is an organization of breeders whose purposes include

Crossbreeding

Crossbreeding is the mating of animals from different breeds

Inbreeding

Inbreeding is the mating of animals more closely related than the average population

Relative importance of the Boar and Sow

Boar:

Sow:

As far as the pig’s genetics are concerned, each parent provides equal genetic forces.

If you have not yet read the discussion of heterosis, please click here. HETEROSIS