The best fence topping would be either several strands of electric farm fence wire or install "coyote rollers."
Basic info about electric fencing to keep coyotes and wolves out:
http://www.zarebasystems.com/learning-center/animal-selector/coyotes-wolves
I have installed a LOT of electric fencing by myself, and it is super easy. Tip: be sure to get a good electric fence tester that shows the strength of the current on your wires, not the cheap one light model.
This PDF file has excellent illustrations and more info:
https://pdfs.semanticscholar.org/6abd/d5b63f6ff6381201ac33b49f8792e58090e6.pdf
About coyote rollers:
The rollers are placed on top of almost any kind of fence to make it difficult for animals to gain a foothold to pull themselves over the top. The roller rotates with as little as 2 ounces of pressure and withstands 250 pounds of weight.
According to the manufacturer (
https://coyoteroller.com/), here’s how it works:
(Quoted from their site)
Our research indicates that a coyote can go over a 6-foot high fence and be in your yard in just over one second! Consequently, it may appear as though the coyote jumped completely over the fence, without touching it. In fact, the "jump" consists of two phases.
First, the coyote jumps to grab hold of the top of the fence with its front paws. The coyote then adds to its vertical momentum by pulling on the top of the fence. This allows him to gain additional height. At the same time, he brings his back paws up to the top of the fence, so that momentary, all four of his paws are in contact with the top of the fence. All of this takes less than half a second!
Next, the coyote then uses his back legs to spring off the fence, while he extends his front paws in preparation for landing. The Coyote Roller interferes with the first part of the jump by making it virtually impossible for the animal to grab the top of the fence. Denied traction, the coyote loses its footing. And combined with the forward momentum, ends up banging into the fence and falling down.
In their demo video,
a coyote-size dog scales a fence easily, but with the Coyote Roller installed he can’t begin to get a foothold. In fact after a few attempts the dog won’t even try.
Coyotes, being highly intelligent animals, would probably bypass the fence after a few tries and seek his snacks someplace else.
Cautionary note if you decide to design and make your own "coyote roller"
Homemade roller systems often fail because the wire/cable is not taut enough to keep the rollers from moving down when any weight is applied to them. This means that when an animal of any reasonable weight uses them for leverage (like a dog or coyote), the PVC falls downward and the animal is STILL ABLE to use the top of the fence to leverage to get over.