Is cow is only mammal who gives oxygen ? why?
Cows is like any other animal which do not produce oxygen as plants do. Cows, like all other animals, inhale oxygen and exhale carbon dioxide. However, the lungs of animals are not efficient to use all oxygen inhaled, so some oxygen that was not absorbed is exhaled. This is the reason behind why mouth-to-mouth resuscitation works.
Usually, almost all animals and humans inhale 21% oxygen and exhale 14–18% oxygen, the difference here reflects that oxygen is exhaled too.