If domestic cats and dogs go vegan, their planet-friendly diet could help to curb global warming, research suggests.
The food energy savings involved from avoiding the mass consumption of ground-up animal meat and bone would also mean billions more people could be fed, according to a major study released by Griffith University Professor Andrew Knight.
The research published on Thursday shows vegan humans and their pets would emit fewer greenhouse gases, save precious fresh water and use less land.
Many studies have pointed to current and projected future livestock consumption as a potent source of global methane as well as being unsustainable because of agriculture's reliance on fossil fuels, fertilisers and pesticides.
"We've long known that plant-based diets are better for the planet but have not seriously considered the impacts of pet food," Prof Knight said.
A higher proportion of dog and cat diets (34.0% per cent and 30.9 per cent of calories respectively) are supplied by animal sources than the average human diet.
He said pet food has profound environmental impacts, which means very large environmental benefits can be achieved by using nutritionally-sound vegan pet food.
Many new vegan pet foods are using plant-based ingredients supplemented with vitamins, amino acids and minerals, to ensure the alternative diet is healthy for the household cat or pooch.
"It is now realistically feasible to examine the potential benefits for environmental sustainability, of nutritionally-sound vegan diets for dogs and cats," the research paper said.
Prof Knight calculated that the world's domesticated cats and dogs consume around seven billion animals or nine per cent of all land animals killed every year for food, as well as billions of fish and aquatic animals.
If dogs went vegan, it would save more emissions than all those emitted by the United Kingdom and the savings could feed Europe.
If all the world's domestic cats went vegan, it would save more emissions than all those emitted by New Zealand and free up land larger than Germany.
And if the world's human population went vegan, an additional 5.3 billion people could be fed, the study found.
"Large-scale studies have also shown that health outcomes for both dogs and cats are as good or better," Prof Knight said.
"And studies of feeding behaviour have demonstrated that average dogs and cats enjoy vegan pet foods as much as those made from meat."
The research has been published in the scientific journal PLOS ONE.
