Some people give up meat due to cruelty but still consume milk and dairy because they assume that these are cruelty free. In reality the dairy industry may be just as cruel as the beef industry, if not, more so.
Milk is produced by a cow only after she has had a calf. The milk is the desired product of breeding the cow, the calf is not. As such the calves are removed from their mother’s so they do not drink the milk (thus there is more milk for collection). The mother cow calls for her calf, she is just as sad as a human mother would be if her baby were taken away at birth. The calf is moved where the mother cannot hear it, and it cries for its mom. The calf is put in a tiny enclosure with barely enough room to move around (it is not allowed to run or play). The calf may be killed at a few days of age (used as bob veal) or at a few weeks of age (veal). Very few are kept to replace the older cows.
Dairy calf, photo property of author
Let’s compare this to the beef industry where calves get to grow up with their mom, usually in huge fields, are weaned at several months of age, and slaughtered months later; dairy calves have a much shorter, and much more boring life, but that is not the only cruelty.
The dairy cows themselves rarely get outside during milking season. Eating grass might change the way their milk tastes, so often they are kept indoors in a cement floored barn or out in a muddy pasture. In fact there are some videos showing dairy cows jumping with glee when finally allowed to go out on pasture for a few months before the cycle starts again.
In some countries (such as the USA) the dairy cows are given hormones to make them produce an abnormally high amount of milk. These hormones also increase her chances of getting mastitis, a painful swelling in the udder, which would usually mean she is culled/slaughtered.
It should be noted that in the UK dairy cows are treated somewhat more humanely than in North America.
The life of a dairy cow is often shorter than that of a beef cow, in that she is usually killed when milk production goes down even though she might still be able to have calves and produce milk. In places where hormones are given to increase her milk production, health issues (such as mastitis) are more common and also contribute to a shorter lifespan as many farmers would just cull such a cow rather than keep her.