Two young spaniels were discovered by a member of the public on Thursday last week and the Scottish SPCA suspects they came from a low welfare puppy farm.
The pups are thought to have been around four weeks old when they were abandoned: one passed away and the other had to be euthanised under veterinary advice.
A Scottish SPCA special investigations inspector, who cannot be named due to undercover operations, explained the discovery of the puppies followed recent seizures of dogs by officers at Cairnryan port.
The investigator said: “Due to the circumstances in which these young spaniels were found, we suspect they may have come from the Cairnryan port as part of the illegal puppy trade.
“In the past we have come across similar cases such as this where any puppies who fall ill on the journey are simply discarded and left to die.
“These young dogs were only four weeks old and should have still been with their mother and littermates.
“Instead they were left to die alone and afraid at the side of the road.
“This is the true cost of the puppy trade.”
The inspector also stressed that the supply for badly-bred puppies will only disappear if public demand stops.
They added: “Every year, thousands of pups are dying at just days or weeks old to fuel the trade.
“We will continue to fight the puppy trade every step of the way, but we need each and every person to do their bit to help us stop it.
“There are thousands of adverts on websites like Gumtree for puppies, but there is no guarantee you are buying from a responsible breeder when you shop online.”
If anyone has any information regarding the puppy trade, or is concerned they may have purchased a pup from a low welfare breeder, they should call our confidential animal helpline on 03000 999 999.