Inbreeding in Dairy Cattle

Inbreeding is defined as half of the genetic relationship between an animal’s parents. For example, the offspring from a mating of animals A and B, which have the same father, will have 12.5 percent inbreeding, because the genetic relationship between A and B is 25 percent. Statistical methods to select the best sires of each generation have been developed, making it feasible to achieve any possible selection goal within a herd. When focusing on only one or few traits, the probability of selecting animals that are related increases [20], generating higher levels of inbreeding. Reporting mean inbreeding coefficient for several breeds from 1965 to 1999, Norman et al. [10] noted that inbreeding levels increased more rapidly after 1980, especially in Jerseys. They also showed that the mean inbreeding coefficient of bulls entering AI progeny test programs ranged from