How is animal blood different from human blood?

Both human blood and animal blood have hemoglobin in it. The hemoglobin binds to oxygen and transports it to myoglobin which is in the muscles. The partial pressure of oxygen for working muscles is less than that for resting muscles, and at this condition of lower pressure, the oxygen's affinity for the hemoglobin lessens. (affinity - the force by which atoms are held together in chemical compounds). The affinity of oxygen to myoglobin at this pressure however is still relatively high, so the oxygen is transferred from the hemoglobin to the myoglobin.

The thing that is different is that humans blood has 2,3-bisphosphoglycerate in it and animal blood such as pig and cow blood does not. The 2,3-bisphosphoglycerate binds to the deoxyhemoglobin and not the oxygenated form. This lowers hemoglobins affinity for oxygen, making the release of the oxygen to the myoglobin easier. It is used to control the transfer of oxygen from hemoglobin to myoglobin more efficiently because then it is not only affected by the partial pressure of the oxygen, but also by the concentration of the 2,3-bisphosphoglycerate.