A shade over the water tank will help keep the tank cool, but don't provide so much shade that cows stay around the tank for relief from the sun. For example, if the tank is located 25 feet above the pump, it will take a little more than 10 psi just to lift the water to that level. This means that starting with a given pressure, there will be 10 pounds less pressure available for pushing water through the pipe. On the other hand, if the tank is 25 feet lower than the pump, there will be 10 pounds more pressure to work with. However, without sufficient pressure at the outlet, water flow will be restricted.
Pressure required at the outlet depends on the type of outlet and control.
Use the manufacturer's rating, if available, for outlet pressure. If unknown, use 3 psi per gallon of flow rate as an approximation. With a 20-40 pound pressure range at the pump and a long run of pipe, pressure at the outlet may be so low at the tank that water will flow out of the pipe very slowly. Continuous flow and tank overflow without control is not recommended. Water is a resource that should not be wasted.