The entire 20 acres has a perimeter fence, and while the front property line is a stone wall, there is fencing running inside it. Why? Because one of the farm dogs used to jump the wall when he was skinnier. He's now too overweight to make the leap, but the fence stays. It comes in handy for keeping the new dairy goats in, and 2 footed snoops out.
The back 14 acres also has cross fencing. That means that it is divided into several separated pasture fields. This is because I use rotational grazing.
So counting all the fencing, it comes very close to 2 miles of fence. Oh geez! It's hard for me to believe I put most of that original fencing up myself. Thank heavens for David, who completed what I started. Yup, the old farm fence was all rotted away when we bought this land. Even the fence posts were well past their lifespans. And now since the time that the fence was put up, it's had to have many repairs here and there over the years. Occasionally a t-post has rusted off at the base, but mostly it's the fencing itself that rusts out. Surprisingly the whole fence doesn't rust away at the same rate. Some sections of my original fence have rusted badly, requiring replacement twice now. Other sections are the original fence. All the same brand and grade fence, so go figure.
Although it was very expensive, I have no regrets fencing in the 20 acres. And the cross fencing, though not mandatory, has been a significant benefit. I may never see a full cash return on the cross fencing in my lifetime, but again, I have no regrets.
A farm surely doesn't need field fencing. There are indeed other options. But field fencing keeps not only my livestock in, but also controls the farm dogs. It's really nice being able to let the dogs run the farm without having to keep an eye on them. Now that the new pup is 6 months old, he can no longer squeeze under the gates, so he's secure now too.