Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853; Department of Veterinary Integrative Biosciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station 77843. Electronic address: [Email]
Our objectives were to evaluate the clinical efficacy of oral and intranasal administration of a commercial modified-live Salmonella Dublin vaccine in dairy calves and to determine the serologic response associated with these extralabel routes of administration. We conducted a randomized field trial with calves from a New York dairy farm following an outbreak of Salmonella Dublin. A total of 399 Holstein calves were allocated by pen to 3 treatment groups: oral vaccination, intranasal vaccination, and an unvaccinated control group. Administration of the vaccine through oral and intranasal routes did not have a significant effect on pneumonia incidence risk or weight gain; however, calves vaccinated orally and intranasally had lower mortality risk as compared with control calves. Among calves tested using a Salmonella Dublin ELISA, vaccination did not induce an increase in antibody production relative to control calves, indicating that oral and intranasal administration will not hinder diagnosis based on this assay.