The research team decided to test the consequences of sperm-free mountings [of chickens by roosters] on a female’s propensity for promiscuity. Using cleverly designed harnesses, which prevent cocks from depositing semen into a females’ reproductive tract, the team was able to create two distinct groups - hens that had been mounted, but received no sperm, and hens who had successful, sperm-transferring copulations.
The point? To examine a remarkable male strategy to keep the hens faithful. It would appear they are far less likely to "stray" to another male's territory as long as they're "getting some" every day.