The present textbook has been designed to serve as a valuable resource for elementary animal physiology courses offered at colleges of agriculture, zoology, veterinary and animal sciences. It is the aim of this textbook to provide a clear and concise explanation of the functioning of the various systems of domestic animals in all its chapters. Whenever deemed appropriate, the textbook has made use of examples from both human and non-domestic animals such as rats and rabbits. As a discipline, physiology has grown to encompass a wide range of topics. The textbook delves deeply into the following areas:The nature and scope of physiologyThe composition and regulation of body fluids, including water, electrolytes, and acid-base balanceRespirationBlood and the circulatory systemThe structure and function of the kidneyThe function of the rumenDigestion and metabolismVitamins and mineralsThe endocrine system and its secretions Reproduction in malesFemale reproductionLactationThe nervous systemThe physiology of bone, skin, and special sensesThe regulation of body temperature.