Willie Nelson has released an open letter to his fans advocating for the protection of the United States' population of free-roaming wild horses.

"Wild horses, like other wild animals, were meant to be wild and free," writes Nelson. In his letter, the country icon urges his fans to contact their Congressional representatives to put pressure on the Bureau of Land Management to end wild horse roundups, increase the use of safe and humane fertility control methods in wild horse populations, and pass the SAFE Act to protect the species he calls "historic symbols of American freedom."

Fifty years ago, Congress voted unanimously to protect land inhabited by wild horse and burro populations with the passage of the Wild Free-Roaming Horses and Burros Act. As Nelson points out in his letter, though, these protections have since been accompanied by regulations that force the horses and burros to "share the protected land with private livestock grazing, energy projects and public recreation," therefore, the singer says, creating conflicting interests for "the Bureau of Land Management, ranchers, energy developers and wild horse advocates."

"Let’s heal our divisions by coming together for this common purpose," Nelson's letter concludes.

Nelson is passionate about animal welfare, and currently houses more than 70 horses at his 700-acre Luck Ranch in Spicewood, Texas.

"My horses are probably the luckiest horses in the world," he recently told the San Antonio broadcast station KSAT. The horses at Luck are hand-fed twice a day, and were rescued by Nelson from a slaughterhouse.

In 2013, Nelson canceled a show planned at SeaWorld for the park's "Bands, Brew and BBQ" series, telling CNN, "I don't agree with the way they treat their animals."

See Pictures of Willie Nelson Through the Years: