Fourteen puppies have been found crammed into two cages and dumped in a field on the Lincolnshire border.
The RSPCA, which was alerted on Sunday, is appealing for information about the case.
A farmer discovered the yelping animals between Claypole and Dry Doddington, near Newark.
The cross-breeds were in a wooden ferret cage and a cat carrier. Six are aged around 14 weeks old and eight are around eight weeks old.
The RSPCA said it was too early to identify what breeds the pups were but it said they could have come from up to three litters.
Some had severe worms and the charity is now providing veterinary treatment.
Animal collection officer Fran Whitten said the animals were packed in "like sardines".
"They just couldn't move," she said. "I was absolutely horrified that someone had put so many in such small containers."
To contact the RSPCA, call 0300 123 8018.