Humans are the only species that will drink the mammary gland extract of another species. And we didn't even choose a species close to us like monkeys or gorillas. No, we've chosen to drink milk from furry, four-legged creatures mostly because they're the easiest ones to control and dope up with synthetic hormones that turn them into milk-generating machines for profit-motivated dairy operations.
All commercial milk from cows contains pus and blood, by the way. The USDA actually sets allowable limits of pus as a federal standard. (Check MilkSucks.com to see how much pus is found in milk in your State!) And that's not to mention the toxic chemicals, PCBs, pesticides, perchlorate and other substances frequently found in milk products. Even if they were somehow free of these chemicals, nearly all commercially-produced milk is pasteurized and homogenized -- a process that turns milk fats into artery-clogging substances that promote heart disease and atherosclerosis.
Yet western populations chug milk by the gallon, and then the people wonder why they suffer from Irritable Bowel Syndrome, obesity, heart disease, sinusitis, acne, constipation and even diabetes. The answer is cow's milk, folks. You'd be better off drinking human milk, but even that's only for babies.
Truly, drinking milk from cows is about as silly as pushing a baby calf away from its mother and sucking on the teat yourself. Which is, of course, the very concept this comic is attempting to portray.