Only One Woof by James Herriot illustrated by Peter Barrett*

Gyp, a sheepdog, loves romping with his brother Sweep.  Their owner, Mr. Wilkin, trains the brothers and eventually sells Sweep.  Gyp proves to be a loyal, sweet companion but is not the skilled sheep dog his brother Sweep is.  A peculiar trait about him is he never barks.
The following summer Mr. Herriot attends a sheepdog trial where he sees both Gyp and Sweep (with their separate owners).  Sweep is competing in the trial and proves very competent.  Will the two brothers recognize each other?
*Highly recommend.
-Borrowed from the library.
Beautiful illustrations.