The Bozeman Daily Chronicle reports Cow No. 403 at Lance and Erika Chaney's ranch near Manhattan gave birth Monday to three 40-pound calves.
The two females and male are all healthy.
Washington State University's College of Veterinary Medicine says the odds of a beef cow having triplets are one in 105,000 births, with longer odds that all three survive.
And Lance Chaney says the cow is nursing all of them, which is rare.
He's a fourth-generation rancher who oversees about 300 Angus cows year-round and several hundred of their offspring each spring. Chaney says the family ranch has had plenty of twins before but never triplets.