Dairy farms have to keep cows lactating year round to be able to produce the greatest amount of milk for the least amount of cost. And if you know anything about human biology, cow biology is no different. When does a woman lactate? When she's pregnant. It's an extremely unnatural lifestyle to live.
Ensuing male newborns (bulls) are discarded as they're basically useless to the dairy industry. Females are used for their milk and the process begins all over again.
Calves are stripped from their mothers at a very early age, which causes them obvious emotional stress. A good portion of those calves are then used for veal, which is made by keeping a baby calf enclosed in a tiny square crate, shackled at the ankles. Restricting movement helps to keep the meat tender. The calf barely moves her entire life. And gets slaughtered at the end of it.
Eggs are a complete mess, but the gist of it is this: hens are often kept in cages so tight that they can barely lift a single wing, and they're fattened up so unnaturally that they die at extremely young ages and live their entire lives as egg-laying machines.
If we raised our dogs the way factory farms raise their chickens, we'd be sent to jail pretty quick.
I'm sparing everyone the images.