My dogs' hair is also trimmed underneath - their bellies and private areas for sanitary reasons. The hair on my retired champion females are kept long on their sides and then trimmed on the top. Just how I like it. Of course the hair on my young girls are long and wrapped to let their hair to continue to grow and to allow them to play and not trip over their coat or get it dirty.
To answer your question - it takes about two years on an average to let a coat grow completly out if cared for and they have a good silky coat. |