Disability-adjusted life years (DALYs) represent the number of healthy life years lost due to disease. They are calculated by combining the years of life lost from premature mortality with the years lived with disability, weighted by a disease-specific severity factor. In this sense, DALYs can be considered the opposite of quality-adjusted life years (QALYs): while QALYs should be maximized for better health, DALYs should be minimized to reduce the impact of disease. Although DALYs were originally developed to evaluate human diseases and guide public health decisions, they have also been adapted for use in animals. The zoonosis DALY (zDALY) expands the human DALY concept to account for the effect of zoonotic diseases in animals. The welfare-adjusted life year (WALY) applies DALY principles to assess welfare loss in veterinary settings. WALYs represent a powerful tool to evaluate welfare compromise and disease impacts in companion and production animals, with wide-ranging potential applications in veterinary health care.