Police say no arrests were made at Monday's noisy but peaceful "Bird of Peace" protest outside Quintiles in Ledbury.
The event was organised to mark the World Month for Laboratory Animals.
The protesters managed to fasten scores of paper doves to Quintiles' perimeter fence, and also coloured ribbons.
Protester Anita Knittel, a member of the Nurses Anti-Vivisection Movement, said: "On the doves were messages to the animals to show that they are not forgotten."
At the height of the protests, just after 5pm, there were more than 20 protesters around the gates.
Police halted the traffic flowing from Ledbury towards Bromyard, allowing Quintiles workers to drive through the opened gates unimpeded.
Ledbury's Police Sergeant, Bob Wilson, said: "The protest didn't cause any difficulties. It was vocal but not physical. That many people make a lot more noise than someone on their own."
Even after the Quintiles workers had driven away, the shouts and the protests continued as the ordinary traffic passed by.
6 Anita Knittel ties a white dove to the fence outside Quintiles.
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