The obvious cause for a fall in the sale of pet food would be a fall in the number of pets, but that's not what's going on here. If anything, millennials are more likely to have a pet than any other generation. They're more likely to be single after all, so they'll keep a dog or a cat for company. As it turns out, they're just a little choosy about what they feed to that dog or cat.
If you're a keen internet browser, you'll have come across the term 'fur baby' before - and it sums up the way many young people treat their pets. Generic pet food from cans is seen as cheap and nasty, and so some millennials - against veterinarian advice, may we add - have taken to preparing their own meals for their pets. Even when they're not doing that, they go for luxury brands to make sure their pet gets nothing but the best. Looking at it another way, the pets of millennials are eating better than their owners!