Lyric discussion by ramthar 

a "blue eyed merle" is a breed of dog, something like a collie, i believe. and although i dont know this for sure, i think that "There ain't no old Shep gonna happen again" may mean that Plant may have once had a sheep dog that the dog in this song didnt like much, and Plant is telling him that he won`t do that to him again. but that is just speculation.

Na, 'old shep' is a depressing american folk ballad about a boy and his dog,the dog gets old and ill and the boy has to shoot it. Extra info- 'old shep' was the first song that Elvis sang competitivly when he was around 12-14 (in a local tallent show in his town, he came second), and there is a reference to the song in only fools and horses, the song is so depressing it empties the pub, lol. Any ways, the lyrics mean 'if you get old... i won't get you put down, we'll carry on the same'

A merle is a type of Border Collie.

There is a type of Australian Shepard called a blue merle. That might be what they're talking about

skhs-australianshepherds.wikispaces.com/file/view/blue_merle_aussie.jpg/78224315/blue_merle_aussie.jpg

An error occured.