The identification of polymorphic microsatellite loci in the horse and their use in thoroughbred parentage testing.

Six new horse microsatellite loci were identified by sequencing M13 clones containing horse genomic inserts which gave positive signals when probed with a CA/GT repeat probe. Oligonucleotide primer pairs were synthesized for these loci and for two previously described horse microsatellites, HTG4 and HTG6. Polymerase chain reaction assays were then carried out on a panel of 20 different unrelated Thoroughbred horse DNAs. DNAs from eight cases of double covering which could not be solved by conventional blood typing were also examined. Several of the loci amplified were found to be polymorphic and, using a limited subset of primers, a clear exclusion could be established for one of the stallions in five of the cases. DNA typing is therefore a useful adjunct to blood typing in the horse and indeed, in the future will probably replace it.