Can my labrador dog mate with my jack russell b*tch?

If you want to save yourself money and stress, I would highly recommend fixing one of your dogs. It is virtually impossible to keep two unfixed dogs from breeding. They don't know it could hurt/kill her, but thankfully you do. Plus after that you can have them play together all day for the rest of their life's and never loose sleep, Isn't that worth the cost of spay?