A movie from around 1970 about a group of kids who see a bison farm and watch as they are slaughtered. They scheme to release the bison. A song in the movie was the theme to The Young and the Restless.

Bless the Beasts & Children (1971) (http://www.imdb.com/title/tt0068286/)

Mr. Adolf_Hilfiger is correct. Sadly, this is a terrible, terrible movie.