09/09/2026
🧬 The Em Gene (Melanistic Mask)
This is one of those really annoying colour genes! I struggled to find information about it in stumpies how it looks on different stumpies/ACD so thought I would share.
It doesn’t affect health in any way, but it can cause the muzzle to be a different colour to the rest of the dog, as the pictures show.
It’s easy to spot on a red dog, while some blue dogs can hide it really well. I was suspicious that Gracie carried a mask, but when she had her DNA testing done, Orivet wasn’t testing for Em on the Australian Stumpy Tail Cattle Dog breed panel at the time.
She had been matched with a male who was DNA clear for all the testable hereditary diseases and Em, so I decided to wait and see what her puppies’ DNA results told us — 2 of the puppies results where 1 copy of Em so this had to come from Gracie.
What makes this gene particularly annoying is that only one copy is needed for the trait to be expressed. So even if you breed an Em carrier to an Em-clear partner, you can still produce puppies that potentially display the mask.
But this is also a great example of why DNA testing is so useful in a breeding program. 🧬
Gracie had 5 puppies, and only 2 inherited the Em gene. The other 3 are genetically clear.
Those clear puppies could then be bred to another Em-clear dog, and they cannot produce puppies carrying the Em gene.
It means we can identify these traits, make informed breeding decisions and gradually breed away from them, without having to remove otherwise valuable dogs from the gene pool.
That’s what I love about genetics.
(Its a shame there isn't a DNA test for ear size... Beacuse that's clearly been past from mother to son 🤪)
