"A large group of protesters climbed under and over fences and made their way towards the track," assistant Chief Constable Tim Mairs said in a statement on Saturday. "Overall, there have been 25 arrests so far across the day and enquiries are continuing."
The race was not delayed and was won by Kitty's Light. Protest group Animal Rising said it was involved in the protests in a statement on social media.
Last week's Grand National was delayed by animal rights protesters, with 118 people arrested, while a Just Stop Oil protestor halted the World Snooker Championship on Monday after he climbed on to a table and scattered a bag of orange powder paint over the green cloth playing surface.
Organisers of Sunday's London Marathon have stepped up security to avoid protests, with environmental activist group Extinction Rebellion agreeing to help guard the race from disruption.
