I'm wondering if anyone originally involved in this discussion is still around or interested anymore. I came across it in my search for the words to a poem I learned as a small girl, called "Plantonio, the Pride of the Plain". The year I found it in one of my older sister's school books was 1952, but I have no idea the year the book was published. I was only 5, but could read well and read anything that came in front of my eyes. As we were quite poor and owned no books to speak of, I knew the only way I could keep this poem I had found and fallen in love with (the common childhood love of horses drove me) was to memorize it.
I repeated it to myself many times through the years, though after all this time a couple of stanzas have become hazy (hence my present search).
It is different in many ways, but the commonality with the songs is obvious. I wonder which actually came first. I didn't bother to learn the author's name, and have not been able to find it.
The first couple of stanzas from the poem are thus:

"I'll tell you a story, there is one I know
Of a horse I once owned in New Mexico:
Swift as an antelope, black as a crow,
The star on his forehead was whiter than snow.

His dark neck was hidden by a long flow of mane.
They called him 'Plantonio, the Pride of the Plain'.

The whole poem is about 12 stanzas. If there is anyone out there who is interested I'll be glad to tell you the stanzas I know.