In 1860, a dog biscuit was developed by a man named James Spratt.

"Spratt’s Meat Fibrine Dog Cakes contained a mix of blended wheat, vegetables, beetroot, and “the dried unsalted gelatinous parts of Prairie Beef”

These biscuits, although labeled as a primary source for pets, were seen as too expensive, and did not have international commercial success that would follow in the 20th century

In 1922, a canned dog food was produced called Ken-L-Ration, and contained horse meat. 19 years later, an estimated 500,000 horses are slaughtered for their meat for canned dog food.

However, the growing popularity of canned foods for pets would see a huge boom in 1950, as the conglomerate General Mills squire Spratts pet biscuit company, and the Purina company is created.

By 1956, the first dry kibble is produced, and 8 years later, pet food lobbying interests within the group 'the pet food institute' engage in media campaigns to create the widespread narrative that specifically created foods for dogs are the only way to feed your pet.

And the rest, is history!

Source: https://www.petfoodinstitute.org/about-pet-food/nutrition/history-of-pet-food/