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Using "Expected Future Inbreeding"
Dairy Pipeline: April 1999
Bennet Cassell
Extension Dairy Scientist, Genetics and Management
Virginia Tech
(540) 231-4762
bcassell@vt.edu
The Virginia Tech AI Sire Summary and the Top Sire List from the February USDA genetic evaluations contain a new piece of information called "Expected Future Inbreeding". The numbers are in percentages and range from about 2.5% for a few bulls with unique ancestry to about 6% for sons of recently popular bulls such as Blackstar. Expected future inbreeding is determined by calculating the average inbreeding that would be caused by mating each AI bull to 600 randomly chosen females from the population. Bulls with the higher values are more closely related to average cows than are bulls with lower values. How should the numbers be used? For producers who want to manage inbreeding by examining the pedigrees of each cow and each prospective mate, they should not be used at all. They represent average inbreeding rather than the inbreeding caused by a specific mating involving known pedigrees. If pedigree information of cows to be bred is unknown, Expected Future Inbreeding tells the producer more than he/she would otherwise know, but not much more. Producers concerned about the effects of inbreeding -- a justifiable concern for all herds, especially those using herd bulls -- must keep accurate pedigree information on their cows and heifers. All inbreeding -- the known and the unknown -- hurts performance, but only accurate and complete pedigree information will enable producers to manage inbreeding and continue to make genetic improvement. Expected Future Inbreeding is included in Extension bull proofs to draw attention of producers to the increasing average relationships between active AI bulls and the cows to which they will be bred. Don't be hesitant to use high ranking bulls with 6% Expected Future Inbreeding in your breeding program, but examine the pedigree of cows to which he is mated before the straw of semen is thawed.