Hastings (?) sisters -- harmony singers at Uncle Rodney's Ranch

The credits onscreen listed the five gals who sing the little harmonization as sisters -- I hope I've remembered the last name correctly as "Hastings" -- but the imdb.com doesn't credit them, even in the full credits. Couldn't immediately come up with anything on them on google either. Are they known? Is that one or more of them nude later in the party scene, or not? I wonder why they didn't get credited here on the imdb?