Passive immunity stimulated by vaccination of dry cows with a Salmonella bacterial extract.

BACKGROUND: Diarrhea because of Salmonella infection is a cause of neonatal calf diarrhea. The stimulation of passive immunity in the calf by vaccinating the dam for Salmonella has shown some success in previous studies; however, there are no data on the use of currently licensed vaccines in the United States. OBJECTIVE: To determine whether vaccinating cows at dry-off with a commercially available Salmonella bacterial extract would stimulate Salmonella-specific antibodies in the colostrum of cows at calving and whether these antibodies would be transferred to the calf. ANIMALS: Sixty Holstein cattle and 59 calves from a herd presumed to be naïve to Salmonella. METHODS: Prospective clinical trial. Thirty cows were vaccinated at dry-off with a Salmonella enterica serovar Newport bacterial extract and again 4 weeks later. An additional 30 cows received only saline. Calves fed fresh colostrum from their dam within 4 hours of birth had blood collected 24 hours later. RESULTS: Vaccinated cattle had increased Salmonella Newport antibody titers at calving in blood (P = .01) and colostrum (P = .011). Calves that received colostrum from vaccinated cattle also had significant increase in Salmonella antibodies (1.04 ± 0.03) as compared to calves born to unvaccinated cows (0.30 ± 0.02). CONCLUSIONS AND CLINICAL IMPORTANCE: The results indicate that the use of a commercially available Salmonella vaccine can stimulate antibodies that are passed on to the calf via colostral transfer. Further studies need to be done to determine whether these antibodies will offer protection against Salmonella challenge.