An official website of the United States government.
<OL> <LI> Determine prevalence of multi-resistant Salmonella in dairy cattle (calves, heifers, lactating cattle, dry cows, and cull cows). <LI> Determine if co-mingling of calves from multiple farms at a heifer feedlot serves as transmission vector for multi-resistant Salmonella back to the dairy.<LI> Examine waste milk for multi-resistant Salmonella prior to use as calf feed.
Approach: This research will be conducted in collaboration with four large commercial dairies in the southwestern United States. These dairies have been sampled on numerous occasions in previous research and found to have a high incidence of lactating cattle shedding Salmonella. Additionally, while the majority of Salmonella isolates recovered were susceptible to the antibiotics examined, most Salmonella Newport isolates and a few Give isolates were multi-resistant. These dairies are located within a small geographical region and managed similarly. All calves are transported to a heifer feedlot located on one of the dairies and raised there until just prior to freshening, at which point they rejoin the herd of origin. This unique design will enable us to examine several routes of potential Salmonella transmission with animals being sampled at multiple time-points and locations. Waste milk samples (approximately 20) will be screened, prior to calf feeding, and examined for multi-resistant Salmonella and other bacteria capable transferring resistance.