It makes a kind of logical sense. Cats eat mice. They are obligate carnivores, so Wild Earth didn’t want to make koji cat food. (In particular, cats need an amino acid called taurine. It comes from meat, but can also be synthesized and added to plant-based kibble.) And mouse cells happen to be some of the best studied thanks to the use of lab mice in science. But lab-grown mouse meat is not a particularly appetizing idea. Pet-food companies advertise their wares as simulacra of human food: chicken and rice medley, purrrfect paella, o’fishally scampi. It’s about appealing to the human as much as the pet.

After Bethencourt boasted of eating his own dog food, I asked if he would eat the mouse meat, and his enthusiasm noticeably cooled. “You know what? Yes,” he said after hesitating. “Once it’s serum-free, I’ll taste it.” (Mammalian cells often require serum derived from fetuses inside slaughtered cows to grow in a lab. Growing cells without it has been a big hurdle for lab-grown meat.) “It doesn’t look particularly appetizing,” he admitted. “It has a kind of runny texture.”

The mouse-meat project has sparked a backlash from vegans, who left a rash of one-star reviews on Wild Earth’s Facebook page.

Lab-grown meat—for humans or pets—remains controversial among vegans. Bethencourt has staked out what he says is a pragmatic stance: It’ll reduce the number of animals who have to die for food. For other vegans though, it comes with a more fundamental problem. Matt Johnson, an organizer for the animal-rights group Direct Action Everywhere (whose members made headlines last year by wrapping themselves in fake blood and plastic to protest a Berkeley butcher shop), put it this way: “It still reinforces this notion that animals exist as commodities, that they exist as an object for us to consume.” He feeds his cat vegan food from Ami.

Tony Buffington, a vet at the UC Davis School of Veterinary Medicine, told me cats and dogs can certainly stay healthy on a vegan diet that contains proper nutrition. (The Association of American Feed Control sets nutrient profiles for cat and dog food.) The nutritional needs of “neutered adult sedentary animals”—to use his words—are not super complicated. But I could tell he still found the idea a bit ridiculous. “There’s an ethical challenge to making others the means to one’s end. To me that’s what people are doing,” he said. “When they’re feeding dogs and cats vegan foods, they’re making dogs and cats abide by their own personal philosophical beliefs.” He also took issue with the term pet parent. “Maybe it’s because I’m a human parent and an animal owner,” he said, “and I’m old.”

He has a point about simply being old. In the past few decades, pets have become ever more cherished and expensive members of the family. Americans collectively spent nearly $70 billion on their pets in 2017, compared to $17 billion in 1994, according to the American Pet Products Association. Pet-food sales have also doubled since 2000, much of that growth in expensive premium brands. Our pets are eating more expensively than ever, and they’re taking up our organic, raw, vegan, and grain-free diets.