Pedigree Completeness and Inbreeding of Foreign BullsPaul VanRaden, George Wiggans, and Mel Tooker
Animal Improvement Programs Laboratory, ARS-USDA, Beltsville, MD 20705-2350
301-504-8334 (voice) ~ 301-504-8092 (fax) ~ email@example.com ~ http://aipl.arsusda.gov/
Precise accounting for inbreeding requires complete and accurate pedigrees. In cooperation with breed associations, Interbull, and foreign data centers, AIPL has obtained complete pedigrees on most foreign bulls of interest. Average levels of bull inbreeding, daughter inbreeding, and expected future inbreeding (EFI) were examined for proven Holstein bulls born since 1994 with USA daughters in at least 10 herds. All variables were obtained from the November 2004 format 38 file. Inbreeding is reported to a 1960 base, and pedigree completeness is traced to ancestors born before 1970. EFI equals half the bull's average relationship to 3-year-old USA cows. Means shown below are by country of origin, which was determined from the preferred Interbull ID. Pedigrees are very complete for bulls from all countries except New Zealand. Surprisingly, means for daughter inbreeding and EFI indicate that USA cows are as related to imported Holstein bulls as they are to domestic bulls from the same birth years. Inbreeding is a problem whether cows are mated to domestic or to imported bulls.
Table 1. Inbreeding statistics for Holstein bulls with USA daughters.
|Country of Origin||Bulls with US daughters||Inbreeding of US daughters||Expected Future Inbreeding||Inbreeding of Bulls||Bull Pedigree Completeness|
Pedigrees are not as complete and inbreeding is not estimated as accurately for some foreign bulls that do not have USA daughters. Foreign ancestors that are missing are assumed to be as related to USA cows as domestic ancestors from the same birth year. More complete pedigrees would be welcome, but the inbreeding adjustments scheduled for February 2005 are applied only to foreign bulls that have USA daughters (the bulls in Table 1). Statistics by country of origin for all bulls are in Table 2. With the possible exceptions of Poland, New Zealand, and Switzerland (CHE), Holstein bulls in all major countries are fairly closely related to USA Holsteins.
Table 2. Inbreeding statistics for all Holstein bulls born since 1994.
|Country of Origin||Number of Bulls||Expected Future Inbreeding||Inbreeding of Bulls||Bull Pedigree Completeness|
Average relationships of bulls to the Canadian cow population are provided by the Canadian Dairy Network (CDN, 2004). Computer mating programs should be used to control inbreeding in all populations because few breeders have time to study pedigrees of the many cows and bulls available for mating.