** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** HEAVY METALS ARE SIGNIFICANT THREATS TO HUMAN AND ANIMAL HEALTH. MEAT PRODUCTION ANIMALS, LIKE CATTLE, CAN BE EXPOSED TO HEAVY METALS BY INGESTING CONTAMINATED FEED AND WATER. IF EXPOSURES ARE HIGH ENOUGH, ANIMALS FAIL TO THRIVE, FAIL TO GAIN WEIGHT, AND ARE MORE SUSCEPTIBLE TO DISEASE. ALSO, METALS MIGHT ENTER THE FOOD CHAIN IN RETAIL MEAT PRODUCTS AND IMPACT HUMAN HEALTH. CURRENTLY, THERE IS LITTLE INFORMATION REGARDING SAFE EXPOSURE LEVELS FOR AG ANIMALS. THIS PROJECT WILL GENERATE THIS IMPORTANT INFORMATION USING CONTROLLED, EXPERIMENTAL EXPOSURES IN GROUPS OF BEEF CATTLE (STEERS). GROUPS OF STEERS WILL BE EXPOSED TO INCREASING DOSES OF HEAVY METALS AND THE LOWEST DOSE AT WHICH THEIR LIVER AND IMMUNE SYSTEMS ARE AFFECTED WILL BE IDENTIFIED. DURING THESE EXPERIMENTS, WE WILL ALSO DETERMINE WHETHER MEAT AND OTHER RETAILS PRODUCTS FROM THESE ANIMALS ACCUMULATE METALS FOLLOWING EXPOSURE.MICROORGANISMS LIVING IN THE GUT OF CATTLE, CALLED THE MICROBIOME, HELP PROTECT THESE ANIMALS FROM TOXIC EFFECTS OF HEAVY METALS AND OTHER CONTAMINANTS. BISON AND CATTLE HAVE SIMILAR GUT MICROBIOMES AND WE KNOW THAT BISON LIVING IN YELLOWSTONE NATIONAL PARK ARE NATURALLY EXPOSED TO VERY HIGH LEVELS OF METALS IN SURFACE WATERS ORIGINATING FROM HOT SPRINGS AND GEYSERS. WE THINK THAT BISON DRINKING WATER WITH HIGH LEVELS OF METALS MIGHT HOST GUT MICROORGANISMS WITH SPECIAL ABILITIES TO DETOXIFY TOXIC METALS. IF SO, THESE MICROORGANISMS MIGHT HELP PRODUCERS MINIMIZE THE METAL EXPOSURE IN THEIR HERDS AND ULTIMATELY MINIMIZE METALS IN THE FOOD CHAIN AND HUMAN EXPOSURE. WE WILL COLLECTED SAMPLES (STOOL AND URINE) FROM EXPOSED AND UNEXPOSED BISON HERDS AND IDENTIFY MICROORGANISMS IMPORTANT FOR DETOXIFYING HEAVY METALS.