Genotype disclosure in the genomics era: roles and responsibilities.

Disclosure of affected breed without disclosure of major progenitors has been the usual practice in scientific papers reporting recessive heritable disorders of cattle. Before molecular genetics, carrier identity could not be used by breeders to control causal mutations because phenotypically normal heterozygotes among genetically related animals could not be detected other than by test mating. Accurate, low-cost DNA tests fundamentally changed this situation. Genomics can provide relief from the old problem of emerging recessive disorders in cattle breeding, but greater transparency of genotype data between breeders is necessary to fully exploit the opportunities for cost-efficient genetic disease control. Effective control of several recessive disorders has been demonstrated in Angus cattle, based entirely on voluntary DNA testing by breeders but mandatory public disclosure of test results and genotype probabilities for all registered animals. When a DNA test is available, major progenitors (particularly bulls from which semen has been distributed) should be identified and disclosed concurrently with the affected breed. As a minimum, whenever possible the closest common ancestors in the pedigrees of the parents of homozygous mutants should be disclosed after confirmation of carrier status. Progenitor disclosure in scientific publications should occur in cooperation with breed societies, which should have the opportunity to advise breeders and initiate management programs before scientific publication. Unless properly managed, genomic enhancement of animal selection using SNP markers may increase inbreeding, co-ancestry and emergence of recessive disorders. The information systems and genotype disclosure policies of some breed societies will be increasingly challenged, particularly with accelerating mutation discovery using next-generation sequencing.