yes Okotoks you are correct - there are multiple mutations that lead to mule foot - not all of them have been identified
you can think of it sort of like the TH mutations - the Improver mutation and the Outcast mutation are both on the same region of the gene but are different - if you breed a TH carrier with the Improver mutation to a TH carrier with the Outcast mutation you can get a TH calf - even though the mutations are not the same
Like wise if you breed an Angus mule foot carrier to a Holstein mule foot carrier you can get a mule foot calf even though the mutations are not the same - the difference with mule foot is that there is incomplete penetrance - meaning the phenotype of the calf is not always the same - can be variable - number of feet affected etc
you can think of it sort of like the TH mutations - the Improver mutation and the Outcast mutation are both on the same region of the gene but are different - if you breed a TH carrier with the Improver mutation to a TH carrier with the Outcast mutation you can get a TH calf - even though the mutations are not the same
Like wise if you breed an Angus mule foot carrier to a Holstein mule foot carrier you can get a mule foot calf even though the mutations are not the same - the difference with mule foot is that there is incomplete penetrance - meaning the phenotype of the calf is not always the same - can be variable - number of feet affected etc