During 1975 and 1976 more than 75 Michigan dairymen reported in their cows subnormal milk production, loss of weight after calving, failure to exhibit estrus or to re-breed as expected as well as a high incidence uterine infections and lameness. Death from undetermined causes ranged between 10 and 15 percent among adult cows and among calves up to 1 year or more in age many failed to grow normally or died from undetermined causes. Analysis of milk and tissue fat for PBB (polybrominated biphenyls) which had been responsible for a similar epidemic in Michigan revealed no detectable traces. Severe dental fluorosis and exostoses of etatarsal bones led to the discovery that mineral suppements containing up to 6300 ppm of fluoride and protein supplements containing up to 1088 ppm fluoride consumed by the cows were responsible for this epidemic.