Shepherds are an abomination

Genesis 46:34 says “That ye shall say, Thy servants' trade hath been about cattle from our youth even until now, both we, and also our fathers: that ye may dwell in the land of Goshen; for every shepherd is an abomination unto the Egyptians” This verse is very strange.  There is no earlier mention of sheep or flocks in this book.  Where did the sheep come from?  The other thing that makes this strange is that the Egyptians had domesticated sheep.  They revered the ram, which has been found buried in sarcophagus in the past.  The Egyptians associated many domestic animals with deities.  But that leads us back to why would the Egyptians think of shepherds as an abomination?  If they had domesticated them they would have had shepherds of their own.