A horse is a horse, of course, of course...
But this is a horse of a completely different color. The first Mr. Ed -- the one in this pilot -- was a chestnut gelding, while the Mr. Ed we are more familiar with was a golden palomino. And this Wilbur is played by Scott McKay rather than Alan Young. Wilbur's wife was played by Sandra White. In fact, in this Bizarro world, Wilbur's last name is Pope, rather than Post. But this pilot (financed by George Burns, with Jack Benny also behind the scenes somewhere) did not sell, so the series was retooled. The plot of this unaired pilot was followed closely by the eventual pilot that did air and the rest is history.
BTW, Mr. Ed was based on a series of sketches written by Walter Brooks (who also penned the wonderful Freddy the Pig series of children's books) that first appeared in Liberty magazine. For those interested, here's some of the original stories by Brooks, courtesy of Internet Archive: