1st episode? different horse

Has anyone seen or remeber the first episode? Have alway`s heard that they used different horses for the photo shoots but was always the same horse for the show, but in 1st episode after wife tells Wilbur he has to get rid of Ed, he asks him if he needs water? Then starts to brush him, it cuts to him all cleaned up. Ed did look a little dirty, but he had a thin white line down his nose and then after cleaning him up? Ed has real thick white line going down the middle of his nose? (that we all came to notice in all the later episodes) Have DVR and keep rewinding to see if dirt was covering up the white line? It wasnt though, it was a totally different horse. Its very plain to see, just wondering if anyone ever heard about a differnt horse in the 1st episode? Dont understand why they couldnt have just dirtied up the REAL Mr. Ed. As far i have read on all the story`s it was always the same horse (except for the picture shoots) dont understand why they would have used a different horse in the very first episode. Just wondering if anyone ever heard about this?