A Montana rancher illegally used tissue and testicles from wild sheep killed by hunters in central Asia and the U.S. to breed “giant” hybrid sheep for sale to private hunting preserves in Texas, according to court documents and federal prosecutors.

Arthur “Jack” Schubarth, 80, of Vaughn, Montana pleaded guilty to felony charges of wildlife trafficking and conspiracy to traffic wildlife during an appearance Tuesday before a federal judge in Great Falls. Each count carries a maximum penalty of five years in prison and a $250,000 fine.

Court documents describe a yearslong conspiracy, beginning in 2013, in which Schubarth and at least five other people sought to create “giant sheep hybrids” by cross-breeding different species. Their goal was to garner high prices from hunting preserves where people shoot captive trophy game animals for a fee.

Using biological tissue obtained from a hunter who killed a wild sheep in Kyrgyzstan belonging to the world’s largest species of the animals — Marco Polo argali sheep — Schubarth procured cloned embryos of the animal from a lab, according to court documents.