matted hair on my aussie sherherd female

Question
i let my dogs hair gett very matted on her backside;  she runs in the brush in
Tahoe and i thought it protected her but now i'm wondering if it is too much
mattedness too thick ;  she is seven years old . . . what should i do?  how is she
to be groomed?  i'm afraid of sun burn or scratching if she is shaved?  how does
a groomer proceed if shaving is in order?  how long does it take for the hair to
come back?  is this the wrong time of year ?  will her hair come back regular?

Answer
Mats hurt, and can actually cause parasites to attack the dog if they tighten too much - groomers will tell you that some dogs have actually been infested with maggots when the mats get too bad and the skin underneath starts to ooze.  So, this is a situation you must remedy right away if the mats are severe.  If the mats are down to the skin, she may need to be shaved, and your groomer can tell you if that's the case.  If she is to be shaved, your groomer will choose the mildest size blade that will do the job, and will change it and use a product like Cool Lube frequently to prevent clipper burns, and will try very hard not to hurt the dog.  If the mats are not down to the skin, and there is any way to brush them out, the groomer can do it, but you may have to pay an extra de-matting/brushing fee.  Make your decision based on the dog's welfare, and allow the groomer to shave the dog if the brushing/de-matting is too stressful for her.  It takes a long time for the hair to grow back, but it will, so do what you have to do for the dog's health.  They do make pet sunscreen:
http://www.funstufffordogs.com/Qstore/Qstore.cgi?CMD=011&PROD=1080228749
Don't worry, her hair will still look pretty good when it does grow back, especially if you then keep up with brushing her often enough.