This article is from the WSSF 2013 AFRMA Rat & Mouse Tales news-magazine.

By Sarah Yeomans, Blackthorn Stud, England

I’d like to talk to you about Dutch mice. You see, a few Americans have admired my Dutch and are sad that Dutch aren’t available to them—but they are! I’m very enthusiastic about them as a variety and want to spread the Dutch love!

I’ve done many test matings to determine the genetics behind them, and I have found that Dutch is just the common recessive spotted ss, rather than the often assumed ‘du’ (as the Dutch rabbit) or even s^du/s^du, which is what I first suspected.

People often think Dutch is a separate gene because it appears to breed true after a Self outcross, when actually ss naturally causes clumping in the pigment around the rump and a blaze marking on the face, which makes it look as if Dutch breeds true. In actual fact, if you outcross a Broken to a Self, you see the same Dutch-type markings appearing in F2 litters and you can breed some pretty good Dutch from those (which I have done). Breeding Dutch from piebalds is a bit easier than breeding Broken from piebalds. Brokens need that rump and face colour almost eliminated except for one or two spots in each area. It takes a lot of breeding to break the patches up into proper Brokens again. Only recessive spotting (ss) makes Dutch (and Broken and most Evens of which are selectively bred to get the markings in the right place). Variegated and Banded won’t make Dutch; avoid putting either into Dutch lines.

Anyway, if people were interested in breeding Dutch, they need only to work with piebalds which exhibit cheek patches and saddles (regardless of any other mis-markings) and selective breeding will get them to Dutch. If you are tempted to breed a new line of Dutch mice, this is how you would go about it:

1. Search breeders and pet shops for piebald mice with saddles and face markings, even if they are covered with other spots or have ragged saddles, but obviously the Dutchier the better. You want to keep darker colours at this stage because it makes early selection that much easier. A pale coloured Dutch won’t show any ear pigment or stops, and you need to see them to ensure you haven’t accidentally bred them out.
2. Breed them together. Try and pair them up so that the faults are not matched (body spots, etc.) and the things you want to keep are matched (saddle, cheek patches, etc.).
3. Keep as many bucks as you have does in order that you can properly match the mice together. I have as many bucks as I have does breeding. Currently I have ten breeding pairs on the go and a few cages of young mice running on. To start up a Dutch project I’d say you’d need at least six pairs, more if you can afford the space. Six pairs will allow you a big enough gene pool that you don’t need to bring in new piebalds and set your work back. Once you’ve got going, you do not want to outcross! If you absolutely have to outcross (and I recommend it only as an absolute last resort), use a Self from a long line of Selfs because this won’t bring in new k-factors or any disposition for markings in the wrong place.
4. Keep breeding the Dutchiest mice together, eliminating those with spots on the shoulder first. Spots near the saddle can be used to keep the saddle line higher up the body because if you discount these as well, the saddle will slip further and further back as you try to get a straight line.
5. Select strictly. Don’t be tempted to keep pretty colours or whatever—keep only the ones that look the most like Dutch. Don’t get distracted—it’ll take quite a few generations to make a Dutch line, so stay focused.
6. Learn the standard for Dutch off by heart, then small faults are less likely to slip past and go back into the gene pool. The cheek markings should be oval and include the ears, but not seep into the whisker bed, down the neck, or under the jaw. The saddle line should be straight all the way round, as close to the middle as possible. The back foot stops should be halfway between the toe tips and hock. The tail stop should be halfway down the tail.
7. This isn’t necessary, but I would recommend keeping photos and notes of your litters and their parents. You’ll be able to look back and see which mice are producing the best, and amend your plan and pairings accordingly.

Make no mistake, this is a long term project with heavy culling of stock needed, but it would be worth it in the end.

I just wanted to share that; I hope the information is of some use to someone!

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