Saddened Parks Trust officials have released a video of two dogs attacking the their herd of sheep at Campbell Park over the weekend.
They say police are investigating the attack, which terrified the herd and resulted in one sheep being bitten.
A Parks Trust spokesman said: "We hope that seeing this video will help ensure that dog owners keep their dogs on leads around sheep and cattle in parks. We believe the owner was caught out by her dog’s instinct to chase, rather than this being a malicious act on the owner’s part, all of which reinforces the message of keeping dogs on leads in grazing areas."
The bitten sheep suffered bruising and muscle swelling and is this week receiving treatment.
The attack comes just weeks after a dog brought six Parks Trust sheep to the ground at old Wolverton, injuring one of them so badly that it had to be destroyed. Police are currently looking at prosecuting that dog's owner.
It is a criminal offence for dogs to worry sheep and as a result of an attack the owner can be fined, incur a criminal record and have the dog confiscated or even destroyed.
The video of the latest attack prompted a string of sympathetic comments on the Parks Trust's Facebook page.
One person said: "I just don't get why people will never learn a simple fact. Some say 'my dog is well trained and always obeys me'. Well, no matter how well trained they are all dogs have the potential to do this when their prey instinct kicks in so at an ytime they are around livestock they must be on a lead."
Another commented: "I am so glad someone caught this on camera. Hopefully they will now be able to catch the stupid owner."
The National Sheep Association says it is every dog’s instinct to chase, even if they are usually obedient and good with other animals.
A spokesman said: "Chasing by dogs can do serious damage to sheep, even if the dog doesn’t catch them. The stress of worrying by dogs can cause sheep to die and pregnant ewes to miscarry their lambs.
"Sheep fleeing from dogs are often killed or seriously injured by their panicked attempts to escape, causing untold damage to fences and field boundaries in the process. Dogs chasing ewes and lambs can cause mis-mothering issues, with lambs dying from starvation or hypothermia when they become separated from their mother and fail to find her again."
Dog bites can cause death in sheep or necessitate large veterinary bills as a result of flies being attracted to the wound and causing infection, says the NSA.
They warn that in some circumstances, farmers are legally entitled to shoot dogs if they are endangering their sheep.
"It is vital that you keep your dog on the lead around livestock, even if you can usually trust it to come to call," said the spokesman.
The Parks Trust grazes its sheep on its land all over MK at certain times of year. Warning signs are always put in place for dog owners.