Lamb pneumonia is a major cause of mortality and poor growth in many sheep flocks and 5 to 15% of lambs in the Cornell flock die from pneumonia during each of the five yearlyl lambing seasons. Although there is a U.S. commercial vaccine labeled for sheep, it is made from bovine organisms and does not appear to work in sheep. In this project, Dr. Chang will produce an autogenous vaccine using organisms cultured from Cornell lambs that die of pneumonia and he will add the leucotoxin that contributes to the disease. Half of the Cornell ewe flock will be vaccinated with the other half serving as controls. About a week prior to the start of each of the five lambing seasons, ewes will be sorted out of the flock for lambing and given a booster if they are in the vaccinated group to supply antibodies to their lambs via colostrum. A subset of 50 lambs randomly from the January and/or March lambing seasons will be vaccinated after weaning with an additional 50 randomly-selected lambs serving as controls. The 100 lambs will be process commercially at 30 to 50 kg live weight to score lung lesions due to pneumonia. Additional data on all lambs will include treatments for pneumonia and deaths due to pneumonia as determined by necropsy. Blood samples will be collected prior to and after vaccination of ewes and lambs to determine anitbody levels. Death loss and lamb treatment data will be be analyzed by binary logistic regression and survival analysis. Growth data and lung scores will be analyzed by analysis of variance.