A system and method are provided for diagnosis of animal respiratory diseases using auscultation techniques. Animal lung sounds are recorded and stored as digitized data. Algorithms are applied to the data producing an output indicative of the health of the animal. Another method determines effectiveness of antibiotics administered to animals based upon observed relationships between lung score categories obtained from auscultation. A comparison is made between sample populations of animals that receive different classifications of antibiotics, and this data is compared to lung score categories observed for each of the animals that received the antibiotics. A statistical analysis is conducted to confirm statistical differences in case fatality rates between lung score categories. Insignificant differences in mortality rates across a range of lung score categories indicates the particular antibiotic administered is not effective, whereas a reduced fatality rate associated with lower lung scores indicates a level of antibiotic effectiveness.