The ideal slope of the shoulder is 45 degrees. To measure slope of the shoulder you must measure the angle of the scapula in relation to the horizon. The slope of the shoulder is always measured against the horizon.
Fly spray is the bane of my co-habitation with horses. I get really annoyed at the cost of fly spray, the fact that it doesn't really work awesome, AND...if I am going to pay for something, it better work in a superior manner than what I could make at home.