To calculate the density of horses per acre on the farm, divide the total number of horses by the total number of acres:
\[ \text{Density of horses per acre} = \frac{\text{Total number of horses}}{\text{Total number of acres}} = \frac{360 \text{ horses}}{60 \text{ acres}} = 6 \text{ horses per acre} \]
Thus, the density of horses on the farm is 6 horses per acre.