In some answer to a question, regarding the stressful life the asker is having in his research environment, somebody wrote in the line of, "Postdocs are free agents, they are not livestock".
As I understand so far, perhaps he wanted to mean that postdocs have the liberty of moving from one research facility to another if the circumstances are not in his favor. Postdocs are not simply "domesticated animals raised in an agricultural setting to produce commodities such as food, fiber, and labor".
Is my understanding correct? Perhaps you would like to supplement a bit more to make the idea clearer.