A natural milk production?
A cow would naturally produce about 7 kg of milk per day for her baby; with present production methods, cows are brought to produce about 27 kg per day for our human consumption! It is interesting to note that we are the only species that drinks the maternal milk of another species. To satisfy our taste for dairy products, the mother cow is literally used as an industrial production machine.
Cows, these social animals with complex intelligence that could naturally live 20 years, are sent to the slaughterhouse at about 4 years old (when their production rate is not profitable anymore), thinned, completely sieved and exhausted. You can easily see the ribs on a dairy cow. For any human mother who has already breastfed, it is easy to understand how this type of production is exhausting. Imagine having to do it all your life with a four time-increased rhythm of production and without any breaks!
Dairy cows will have multiple pregnancies throughout their life without ever knowing their babies. And for most of them, they will have been immobilized with a metal harness over their neck and will be kept inside for the entirety of their short life.
Is it worth it for a glass of milk? You can help stop the cruelty by not encouraging the industry.