BBR DNA Tests for Cattle Breeds
white paper report

Breed Base Representation (BBR) is a DNA test to establish relative genetic purity of an animal. "Since the 1800s, breed registries have been established for livestock species to maintain the purity of breeds and to document the ancestry of animals. However, a significant number of animals are unregistered with no or incomplete pedigree data and uncertain ancestral breed origin. Although many heritage livestock breeds are “at risk” on the basis of the number of fullblood breeding females in a breed registry, there is often also a reservoir of unregistered animals that may belong to the same breed. However, due to the missing pedigree it is not possible for breed societies or herd books to include those animals in their closed herd books for pure animals." In 2018 a genetic SNP test was developed to unequivocally determine the breed origin of cattle without pedigree data. This test opens up the possibility to incorporate animals without pedigree data in the breed registry that turn out to be purebred based on the test results. ~ BBR test developers in the Netherlands

Purebred Dairy Cattle Association, member, CDCB

BBR Dairy DNA test. There is currently a BBR test available for 5 dairy breeds; Ayrshire (AY), Brown Swiss (BS), Guernsey (GU), Holstein (HO) and Jersey (JE). The Council of Dairy Cattle Breeding (CDCB) owns these proprietary BBR tests. They had them developed to assess the degree to which alleles in one individual dairy animal's genome are in common with the allele frequency of any of the 5 reference breed groups. CDCB made the decision that animals with a BBR score of greater than or equal to 94 for 1 of the 5 testing dairy breeds are considered to have one-breed background and will be categorized as 100% for that breed, and other possible breed percentages will be set to zero. BBRs below 94 are reported at the % calculated. Precise percentages of breed sources are not possible because of genetic variations that exist within the same breed. And although there are common alleles within breeds, there are also common alleles across breeds. The genetic contribution from a primary breed could be off by 5% or even more. If any breeds other than those 5 are part of the animal’s ancestry then the BBR crossbred test will not be accurate. A BBR score of lower than 90 however, usually indicates crossbreeding. (~ CDCB tools for the improvement of the Jersey breed, 06-2018, worldjerseycattle.com.) The CDCB BBR DNA test is available to the public, at the time of this report, costing owners approximately $25 /cow, $135 /young bull, or close to $1600 /bull over 14 mos.

 

 

More about the CDCB BBR test:
There is evidence that BBR DNA testing results are impacted by the chip used for genotyping. Animals with alleles coming from other breeds (e.g., BBR of the primary breed around 87%) often receive a BBR about 4% higher if re-genotyped using a higher density chip. However if the BBR is above 97% for the primary breed (common for pure animals) there is no consistent change when re-genotyped with a higher density chip. ~ (Documenting changes in dairy breeds in the United States including genomic examination using breed base representation, 2018; H.D. Norman, J.M. Megonigal, G.R. Wiggans, and João Dürr) ~ ICAR

The CDCB BBR test uses 2 approaches, one for purebreds and one for crossbred dairy cattle. The BBR test for a single breed is used on animals that are identified by a breed SNP-based check. The BBR test approach for crossbreeds is designed to determine the % of DNA contributed to the animal by each of the 5 breeds, in order to provide more accurate genomic production evaluation of crossbred dairy animals. If a crossbred animal carries genetics from a breed other than the primary 5 dairy breeds, the results may not be reliable. In April 2019, an updated BBR procedure was developed to lend more accuracy in determining the composition of the 5 dairy breed makeup of crossbreeds. (~CDCB BBRs & Crossbred Dairy Cattle).

 

 

The Accuracy of a BBR Test: We get lots of inquiries about the BBR test, that usually boil down to these questions:

Q: Does a BBR test prove my animal is pure?
A: The short answer is, while a BBR test establishes relative purity, it can not absolutely prove an animal is 100% pure. But if a BBR shows a high enough score for the breed being tested, it provides genetic corroboration for an animal with evidence of purity. Other indications that an animal is pure may include:

1. the animal has an extended pedigree tracing all the way back to the breed's foundation (herdbooks began forming in UK in the early 1800s)
2. the animal displays a phenotype consistent with the history of its breed (irregardless of selection)
3. the animal DNA tests with a genotype consistent with the history of its breed (irregardless of selection)
4. the animal DNA tests with no genotypic traits inconsistent with its history, and known to originate in other breeds

Q: Can I BBR test my cow to find out what breed(s) she is?
A: The short answer is yes and no.
Yes, if she is a purebred or a crossbred of the 5 primary dairy breeds, and does not carry additional genetics of other breeds, and is tested with the CDCB BBR dairy breed test.
No, not if she is tested with a BBR test formulated for breed(s) other than what she is. A BBR test formulated for one breed does not work for another breed. Each breed needs its own BBR test to determine the percentage of that breed's DNA in an animal. If an animal had an unknown pedigree, we could only guess which BBR test(s) to use. As we know, the proprietary CDCB BBR test is formulated for 5 major dairy breeds only. All other breeds of cattle will have to formulate a BBR test of their own.

Q: When formulating a BBR test, how are animals selected to represent a breed?
A: The short answer is, for any existing BBR test we would not know unless we were involved. But when planning a new BBR test for a breed, we know how they should be selected:

1. People entrusted to select a breed base reference population must be experienced with the breed and sufficiently knowledgeable about genetics.
2. People entrusted to select a breed base reference population must be completely objective and free of prejudice or personal agenda regarding purity.
3. Animals selected to represent a breed must be reasonably believed to be 100% pure, with genotype & phenotype consistent with the breed's history.
4. Animals selected to represent a breed should have extended pedigrees indicating stacked generations of purity as far back as the breed has been recorded.
5. Animals selected to represent a breed should be taken from as many diverse populations of pure animals that can be found across the globe.
6. Animals selected to represent a breed base reference population should total in the highest number possible. The more animals used, the more accurate a BBR test should be.

BBR DNA tests made for more breeds of cattle will certainly be developed. There is another one or two that have been developed or are in development for rare heritage breeds. Rare breeds would benefit with added genetic diversity, if found among additional pure (unregistered) cattle identified and included for preservation. There are also mainstream breeds that are no longer believed to be pure, with purity issues debated about animals registered as fullbloods in their main herdbooks. BBR presents a solution to will help protect old pure lines or rare breeds of cattle. However developing the initial BBR test for a breed, could be a major undertaking.