THE USE OF ANTIMICROBIALS IN FOOD ANIMAL PRODUCTION IS OF INCREASING SOCIETAL IMPORTANCE. IN THE BEEF CATTLE INDUSTRY, BOVINE ANAPLASMOSIS IS AN IMPORTANT, PRODUCTION-LIMITING DISEASE THAT PARTICULARLY AFFECTS THE COW-CALF SECTOR. CURRENTLY, PRODUCERS AND VETERINARIANS RELY ON THE USE OF THE ANTIBIOTIC CHLORTETRACYCLINE (CTC) TO CONTROL ACTIVE OUTBREAKS OF BOVINE ANAPLASMOSIS. CHLORTETRACYCLINE IS MOST OFTEN PROVIDED TO BEEF COWS ON PASTURE BY INCLUDING IT IN MINERAL SUPPLEMENT THAT IS OFFERED FREE-CHOICE (I.E., THE COW CAN CHOOSE TO CONSUME THE CTC-MEDICATED MINERAL OR NOT AT ANY TIME). PROBLEMS WITH THIS METHOD OF DELIVERY INCLUDE THE INABILITY OF THE PRODUCER TO ENSURE THAT EACH COW RECEIVES AN INTENDED DOSE OF CTC EACH DAY, AND IF CATTLE DO NOT CONSUME THE INTENDED DOSE, THE CTC MAY NOT HAVE ITS INTENDED EFFECT OF REDUCING ILLNESS AND DEATH DUE TO BOVINE ANAPLASMOSIS. ADDITIONALLY, IF CATTLE CONTINUOUSLY CONSUME LESS THAN THE INTENDED DOSE OF CTC IN A MEDICATED MINERAL SUPPLEMENT, BACTERIAL RESISTANCE TO CTC MAY DEVELOP OVER TIME.THIS PROJECT INTENDS TO MEASURE THE AMOUNT OF CTC-MEDICATED MINERAL THAT CATTLE ON PASTURE VOLUNTARILY CONSUME OVER TIME, AND SUBSEQUENTLY CALCULATE THE DOSE OF CTC RECEIVED. WITH THIS KNOWLEDGE, WE WILL ALSO COLLECT BLOOD SAMPLES FROM THE CATTLE, AND MEASURE THE CONCENTRATION OF CTC WITHIN THE PLASMA TO DETERMINE AVERAGE AMOUNTS OF CTC WITHIN THE BLOOD OF THE ANIMAL. FURTHER, WE WILL COLLECT FECAL SAMPLES AND NASAL SWABS TO INVESTIGATE THE DIFFERENCE IN THE MICROBIAL POPULATIONS OF THE RESPIRATORY AND GASTROINTESTINAL TRACTS OF ANIMALS BEING FED A CTC-MEDICATED MINERAL COMPARED TO THOSE FED AND NON-CTC-MEDICATED MINERAL. THE ULTIMATE GOALS OF THIS PROJECT ARE TO IMPROVE THE COLLECTIVE KNOWLEDGE OF BEST PRACTICES FOR REDUCING ILLNESS AND DEATH IN COW-CALF HERDS DUE TO BOVINE ANAPLASMOSIS, WHILE ALSO IMPROVING ANTIMICROBIAL STEWARDSHIP IN BEEF COW-CALF HERDS. OUR TEAM HOPES TO PROVIDE VETERINARIANS AND BEEF CATTLE PRODUCERS WITH INFORMATION THAT CAN BE USED WHEN DESIGNING PROGRAMS AND STRATEGIES FOR REDUCING THE RISK OF ILLNESS AND DEATH DUE TO BOVINE ANAPLASMOSIS.