The mitochondrial haplotype of thoroughbred racehorses often disagree with stud book records. Thoroughbred performance may depend on the mit

For some time now we have been of the opinion that there has been over selection of the paternal side of the pedigree and under selection of the maternal side of the pedigree in thoroughbred breeding. That is, with large books and better veterinary practice, the bar to become a stallion has probably moved up a little too high (you are just about required to be a GI winner now to have any chance) while because of the same quest for large stallion books, the bar for a mare to