While I have only been to small farms, I have definitely seen what some people would consider animal cruelty. But I think it's important to understand the mentality of people that work with these animals.
Animals on farms are seen as property, not a pet in any way. Most owners and workers of animals distance themselves from the animals to keep themselves mentally healthy as they will be putting these animals to slaughter to sell or eat. When distance yourself from an animal, you won't be treating it as nicely as you would your family dog.
When talking about farm help, they may hold a grudge against the animals they are working with. A friend would work his uncle's farm every saturday to help clean up after the pigs. His job was basically shoveling pig poop for 8 hours (or other equally not-fun jobs). It would take a day before he smelled normal again. Doing this kind of work can make some people resentful of the animals they work with.
Farmers and farm help see animals as money, so they won't do anything that could jeopardize being paid (won't damage the product).
When people are disconnected with the animals they are working with, it is easier for some people not to be so nice to those animals. This isn't to say that all people working with animals will be abusive towards them, but it creates an opening for those people that aren't as nice to take their anger out on the animals.