Police were called to the scene on Tuesday, March 4 following calls from members of the public at around 3.30pm saying they had spotted loose horses in the area.
The horses were eventually located on the local authority’s land.
Officers closed a nearby road to ensure the safety of the public and the incident was dealt with by Three Rivers District Council.
A spokesman for Three Rivers District Council said: "The decision to put the horses down was made very reluctantly."
Attempts were made to find the owners but no one came forward. If captured, the horses would have been held for 14 days.
Rebecca Emmett, Head of Regulatory Services, said: "Two unregistered stray horses which were galloping unsupervised in the Country Park were put down following a four hour attempt by the police and the district council to capture them.
"The horses were an immediate danger to dog walkers and to children in the park and were at risk of straying onto the A41, Woodside Road, East Lane or College Road. The decision to put down the horses was made reluctantly in the interests of the safety of the public. This was undertaken quickly and humanely under careful supervision."