The pilot stated that the purpose of the flight was to conduct low-level aerial operations for cattle herding. The pilot maneuvered the helicopter in an effort to keep the cattle close together and did not notice a phone line in the helicopter's flight path. The main rotor blades contacted the lines and they became entangled in the main rotor head. The helicopter descended from approximately 15 feet above ground level and impacted the terrain hard, collapsing the skids. As a result of the impact, the helicopter sustained substantial damage to both the tail and main rotor blades. The pilot reported no preimpact mechanical malfunctions or failure with the helicopter that would have precluded normal operation.