hi everyone, I'm new here. Got some questions for those more advanced breeders.

I'm pretty good at color genetics 101, but while I'm researching the advanced stuff, maybe you all can answer some questions. I'm guessing that breeding a blue merle with a brown/black brindle will not cause any weirdo lethal white problems, right??????? Isn't it totally different genetic composition? What would be the likely outcome, would there be any brindle pups, any merle pups, etc?

Also, is it totally unusual for a bitch to not show signs of heat upto 17 or 18 months? Would it be more likely that she is maturing slowly or that she is having dry heats?

[Kingsbridge Cav]

I'm not familiar with the color combo you mentioned, so I'll leave it up to someone more informed. I breed Cavalier King Charles spaniels. In my breed it is not advised to cross over from a parti colored (patches) dog to a solid. The result is often pups that are solid with a patch of white where it doesn't belong. The breed standard does not allow for this and technically these pups should not be registrable. Unfortunately, the registration clubs rely on the honesty of the breeder when they are registering.
Any time you breed a pair of dogs it should be to enhance the breed and to strengthen the genetics. The breed standard for your breed is a blueprint for what you should be breeding for, with animal health a primary concern also. Check out your breed specifically. Some of the breed specific books will give you a good idea of what combinations to avoid. If you bought from a reputable breeder, they may be able to answer some of your concerns. If you did not buy from a breeder, but through a pet shop or similar, try finding a breeder of your breed who may take you under their wing. Browse through a website like puppyfind.com to find other breeders in your area.

Silent heats can happen for many months or even all of a bitch's life. She may also not be coming into season at all. Having a virile male on site occasionally may bring her into heat. You may also try housing her with another bitch that does season regularly. It's even better if you know when the other bitch is due to have her heat cycle. It is called a dormitory effect and can be effective if you are having trouble.
I have known females that don't cycle until 3 years old and then regularly every 6 months or so.
Chin up; there are a few tricks you can try!

Breeding merle to brindle won't result in lethal white, or double merle. Both patterns are governed by different alleles.

What you get could be a hodge podge, though. Sure, you might get brindle, you might get merle. You might even get brindle merle. What other colors you might get depends on whatever recessives both dogs carry.

If the merle is blue, you could get black or black brindle. If your brindle is genetic red, you could get red merle, which can be problematic. It won't affect the health of the puppy, but red merles often only show the merling at birth. By the time they're adults, you can't tell. So it would be possible to do a merle to merle breeding without intending to, if one decided to breed that pup when it's an adult.

Personally, I don't think I'd do it, unless both dogs had outstanding qualities, and there wasn't another dog with outstanding qualities available.