Inbreeding takes place when related animals, a sire and a dam, are mated. Then their offspring is inbred. When the sire is inbred and the dam is inbred, but they share no common ancestors, they are not related, thus their offspring is not inbred. In other words inbreeding is not heritable. When a male from another breed is used in a population that male has no common ancestors with any of the females in the breed at stake. Even when this breed has a high average coefficient of inbreeding all the offspring of the “foreign” sire has an inbreeding coefficient of zero. An outcross is very effective to reduce inbreeding and to reduce the inbreeding problems. The outcross can be illustrated with the pedigree of an individual animal where the sire and dam are not related.
In the pedigree of Naen below, the sire Ferdinand is inbred: his parents Tsjalling and Crisje share Ritske P and Bouke P as common ancestors. The dam Truus is inbred: her parents Kerst and Klasine share Ynte as common ancestor. But, based on the 5 generations in this pedigree the son Naen of Ferdinand and Truus is not inbred because Ferdinand and Truus are not related: they do not share a common ancestor. Practical breeders call such a mating within a breed often an “outcross”.
