The blue heeler I adopted in June this year came home from a couple of months at the animal shelter. Her black and white (merle) coat was a mess, filled with grit and dry skin and who knows what - I guess it could have been from before she got there, but they stay in concrete enclosures and go out into an almost grassless space to take care of business. Whatever the reason, she went into the tub and got a thorough scrub and rinse with the vet dog and horse shampoo I keep for this use. She hasn't needed another bath since then and her coat looks good, no buildup of crud. I think a healthier life and lots of exercise and rolling on the lawn has made the difference.