There always seems to be great opposition to the discussion of slavery when it includes multiple types of slavery. Most individuals I speak to are very content keeping to the traditional ideas of slavery, namely the Atlantic slave trade and the Holocaust. These examples are both important and extreme but are not alone in enslaving groups of individuals.
Wage slavery is the dominant structural form of slavery in our economic system. The most obvious examples include natural rubber workers in Liberia. These rubber plantations are owned and operated by massive tire corporations that provide almost every tire on the road today. The employees are paid so little and worked so hard that they are forced to bring their children at night to help them get a start on the day. Liberia has an unemployment rate that hovers around 80% which prevents them from leaving the plantation due to work conditions. The wage they earn is only enough to provide the basics for their families, but not even enough for clean water. This is wage slavery, it happens in every capitalist country and targets the working poor almost exclusively.
There must be mention of the largest form of physical slavery that has ever existed on the face of the Earth - and it is happening right now. The agricultural complex murders tens of billions of individuals every year to provide wasteful, unhealthy products to both unknowing and uncaring consumers. The individuals killed are sentient, they have the ability to feel pain and suffer greatly both physically and mentally from the process. The amount of individuals killed in a single day by this system dwarfs both the Atlantic slave trade and the Holocaust. This is not to devalue anything surrounding the Atlantic slave trade and the Holocaust. They are both horrific experiences in human history, but just because they are important doesn't mean that all other forms of slavery should go without critique.
Animals in the agriculture business are slaves because:
-they do not want to be slaves
-in addition, they do not want to die
-they do not have free mobility
-they are sentient
-they suffer physically and mentally
-they are profited off of by few
-perceived benefits to some are used to justify their slavery
-their social structures and natural behaviour are denied
Whether or not you value other species is often a cultural or nurtured adaptation. Either way, both forms discussed are still slavery. There is no way around it.