A dairy farmer wants to mix a $75 \%$ protein supplement and a standard $25 \%$ protein ration to make 1500 pounds of a high-grade $45 \%$ protein ration. How many pounds of each should he use?

Step 1 ：Let's denote the amount of the 75% protein feed as x and the amount of the 25% protein feed as y. We then have two equations:

Step 2 ：The total weight of the mixture is 1500 pounds: \(x + y = 1500\)

Step 3 ：The total protein in the mixture is 45% of the total weight: \(0.75x + 0.25y = 0.45 * 1500\)

Step 4 ：We can solve these two equations to find the values of x and y.

Step 5 ：By solving the equations, we get \(x = 600.000000000000\) and \(y = 900.000000000000\)

Step 6 ：Final Answer: The dairy farmer should use \(\boxed{600}\) pounds of the 75% protein supplement and \(\boxed{900}\) pounds of the standard 25% protein ration.