Mr. Frei said the switch was also partly for economic reasons. But Melissa Martellotti, a brand communications manager for Mars Petcare US, which makes the Pedigree brand, said that Westminster had initiated the split and that dog show officials told the pet food company that its decision involved concerns about the ad campaign.

“They’ve shared with us, when we parted ways, that they felt that our advertising was focused too much on the cause of adoption and that wasn’t really a shared vision,” she said. The kennel club, she said, is “focused on the purebred mission,” including the adoption of pure breeds as opposed to mixed breeds.

Sandra DeFeo, the executive director of the Humane Society of New York, said, “If you want animals to be adopted, then you want to present it in the best possible way.” She said clients request that she omit disturbing pictures from the society’s newsletter. “It’s all about shedding a beautiful light so that that dog or that cat gets adopted, so that people really see how wonderful they are.”

The fashion photographer Richard Phibbs has recently begun shooting the images of animals that the society features on its Web site. “People need to know that animals are euthanized and that they are suffering,” Ms. DeFeo said. “But I don’t know that people can always handle that.”