Illegal tail docking on dogs will not be tolerated – that is the stark warning sent out by animal welfare officials after a farmer was convicted of the offence yesterday.

Mark Royce Chambers, 25, of Rotsea, Hutton Cranswick, was ordered to pay more than 500 after being found guilty of allowing, or failing to prevent, someone docking the tails of his puppies without any medical reason.

RSPCA inspector Hannah Bryer said: "It sends out a warning to others. It's a problem we have with farmers who know the legislation and continue to breach it – this shows they won't get away with it."

Beverley Magistrates' Court heard the tails of Chambers' black and white male terrier puppy called Zak, a black and white female puppy called Jess and a black and white male terrier puppy called Oliver were docked to between 7cm and 8cm from the base.

Summarising the case, District Judge Daniel Curtis said: "The docked tails were discovered when two of the puppies, Zak and Oliver, were sold to a couple who took them to a local vet to be checked over. The vet noticed the tails were shorter than expected and when the new owners told him they did not have any docking certificates the RSPCA was alerted."

The court heard when first interviewed by Miss Bryer, Chambers claimed the puppies' tails had been chewed off by the mother and a fourth puppy had died as a result of mutilation.

Throughout the trial, the court heard from a number of animal experts, with independent animal behaviour expert Annette Conn telling the court that, after 40 years of research, the chances of a mother chewing the tails of all three puppies was "highly improbable".

Passing sentence, District Judge Curtis said: "Docking tails of puppies is a serious matter. The law changed some time ago and I'm quite sure you are aware that law has changed.

"It is no longer possible, without veterinary examination and certification, for you to do this practise or invite anybody else to do so. Anyone doing so runs the risk of being sent to prison."

Chambers was fined 250, ordered to pay court costs of 250 and a victim surcharge of 15. The judge also ordered that the third puppy Jess should remain in the care of the RSPCA.

An RSPCA spokesman said: "Amputating a dog's tail – by cutting through or crushing skin, muscles, up to seven pairs of nerves, bone and cartilage connections – causes considerable pain.

"Such an operation should not be undertaken without just cause, only, for example, as a result of severe injury or disease."