A plane with a banner including the words 'Cats Lives Matter' was flown over Anfield ahead of West Ham's game against Liverpool on Saturday evening.
West Ham are continuing to select Kurt Zouma despite a video having been posted online last month of the defender kicking and slapping his pet cat.
Zouma was named in the starting lineup by David Moyes for the game against Liverpool.
Shortly after footage of the incident emerged the RSPCA confirmed that Zouma's cats had been taken away from him.
West Ham condemned Zouma's actions and reportedly fined him two weeks' wages, worth £250,000, with the money being donated to animal welfare charities.
Zouma's brother Yoan, who was also present in the video, was suspended by Dagenham & Redbridge.
The fixture against Liverpool was the fifth game Zouma had featured in since the video was posted.
In his first appearance since the incident, Zouma was booed by both West Ham and Watford supporters.
Zouma had been due to start against Leicester City on February 13 but withdrew from the game due to illness.
Last month Moyes revealed that club captain Mark Noble had organised a team meeting to address the situation with Zouma.