If you are going to use dogs to keep coyotes away I would suggest getting at least two larger sized dogs.
In my parents old neighborhood coyotes jumped the fences of the houses bordering the woods and killed 9 dogs, some of them pretty large in a two week period back in the 90's.
I had my favorite dog, a little, Australian shepherd/Australian cattle dog/feist named Dingle go after two coyotes behind my friends barn at around 3:00PM in the afternoon last year.
She went running out the door, while I was working on a pigeon loft in the barn. I ran to the door and she was 10 feet from one coyote and had another one running at her from the side.
I ran out yelling and the one in front of her disapeared.
The other one went up on the hill and then ran back within 30 feet of us as I grabbed Dingle.
It then ran back up on the hill and actually sat and watched us for a few seconds before moving farther away.
I ran to the house and told my friend, James, to grab his 7 mm.
By the time he got it loaded the coyote was standing out in the open on the end of the hay field by the beans. James went to shoot and then dropped the gun down.
One of the deer hunters had a stand right in line with where the coyote was standing.
I ran to the milkhouse to see if the hunter had signed in and he pulled into the driveway as I got there.
The coyote took of before I got back.
I was talking to a farmer I know, Paul, last week. He had his beagle killed and eaten by the coyotes and his German shepherd female torn up within 40 yards of his house.
Keith