Singer's Equation for Deserving Rights.
A body or group + The act of suffering + The capability to prevent the suffering = The need to have rights or take action to protect them.

This equation is an accurate interpretation of Singer's thinking for the following reasons. (I just finished my APUSH reading about the constitution and this set up just feels right) This whole equation is based on the presence of a body of things that are being oppressed. Without a discriminated against group, there is no problem, or necessity for action. Then the act of suffering is what is really the cause of the whole problem of rights. There has to be oppression upon that body to display the need for protection of the rights that body is entitled too. When there is suffering in this instance, there is an oppressor, (us in Singer's essay) and the oppressed (animals). This one sided destruction is what leads to the deficiency of rights. Finally, if the suffering this oppressor causes can be prevented, or avoided, then action must be taken. From the animal rights prospective here, the fact that all animal abuse for the sake of food can be avoided is the prime example of this variable of the equation. In the presence of all of these variables, The need for the protection of rights must be fulfilled,  and steps must be taken because the oppressed deserve their liberties to be shielded from the oppressors.