Ranching is often a family business. Typical story: some dude came over from the East hundreds of years ago and bought himself some land and cattle out West. When he kicked the bucket, his son took over the ranch. When that guy kicked the bucket, his son took over the ranch. When that guy kicked the bucket, his daughter stepped in, because by then it was no big deal for a lady to lead the ranch.
In other words, for most of its existence ranching has been something you picked up from other people. If you were born into a ranching family, you likely stayed a rancher, simply because you had years of hands-on experience to draw from.
Today things are a bit different. Experience still matters, but in a world where technology plays an ever-larger role in agribusiness, you might find you actually need a college degree in order to understand every aspect of ranching.
This is where land-grant colleges and universities come in. Every state has one, and it's the school you go to if you want to earn a degree in animal science.
In an animal science program, you'll study subjects such as animal behavior, beef cattle, equine science, meat science, sheep and goats, animal biotechnology, dairy science, food science and technology, physiology of reproduction, and swine—basically every aspect of life lived as a rancher in the 21st century (source).
Well, except maybe country music appreciation, but you might be able to take that as an elective.