A number of buses in London and Bristol have been plastered with anti-dairy posters.
The images are part of a campaign by animal charity Viva! - encouraging people to stop consuming cow's milk.
According to a spokesperson for the charity: "The message is clear - humans are not designed to consume any milk or dairy products after infancy, and certainly not the milk from another species!
"It’s why up to 75 percent of the world’s population is lactose intolerant in adulthood."
The ads also reveal some facts about the dairy industry which most people don’t know – the shooting of baby male calves, for instance, and the fact that most milk comes from hormone-laden pregnant cows.
Viva! campaigner, Veronika Powell, says: "The aim of the adverts is to highlight that people are not meant to consume cow’s milk. We also want to educate people about the sad realities of the dairy industry."
She adds: "The lifecycle of a dairy cow is a continual exploitation of the female reproductive system. She is artificially inseminated at a young age, carries her baby for nine months, only for the calf to be ripped away from her hours after birth.
"Male calves are useless to the industry, and they are shot shortly after birth or used for veal or cheap beef. Female calves face the same fate as their mothers - a lifetime of pregnancy and exploitation.
"These practices are standard across the dairy industry, regardless of whether the dairy farm is organic or zero-grazing."