Animal physiology is the study of the internal physical and chemical functions of animals. Professionals in this field may explore the makeup of animals, including their genetics, behaviours and their biological structure. A degree in animal physiology can lead to opportunities in a wide variety of areas, including fisheries, veterinary sciences and pharmaceutical research. This book entitled “Animal Physiology” consists of 25 chapters. The chapters are mainly focused on the physiological changes in the animals when exposed to toxicants, drugs, phytochemicals, etc., The authors have put an effort to explain each and every point of respective studies. This book has been brought to the society, keeping in mind students of graduate and post graduate, research scholars and teaching faculty.