The paper deals with animal welfare definitions and animal welfare assessment. Animal welfare is a prolonged mental state, resulting from how the animal experiences its environment over time. There are different methods for animal welfare assessment. The four basic criteria for animal welfare assessment are feeding, housing, health and appropriate behavior. Therefore, criteria used to assess animal welfare are not direct measures of the mental state but only parameters that need to be interpreted in terms of welfare. The immediate housing environment and feeding may influence animal welfare either positively, when most of the important requirements are respected, or negatively, when animals are exposed to various stress factors and unpleasant emotions that contribute to animal disease, injuries or inappropriate behavior. Therefore, animal welfare is a unique link between housing conditions, feeding and watering on one side, and animal health status and behavior on the other side.