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Kansas State University Study

Salmonella Vetovax™ SRP® Vaccine Trial at Kansas State University

  • 180 cows enrolled from a 1,200 Holstein cow herd in Northern Kansas
  • S. Agona isolated in trial cows
  • Clinical salmonellosis apparent in neonatal calves, but not in cows
  • Randomized in pairs: heifers and dry cows included
  • 75 animals vaccinated with Salmonella Vetovax™ SRP®
  • Vaccine booster 21 to 35 days after primary dose
    • Booster 14 to 21 days before parturition
  • Paired set of 75 controls given placebo
  • All cows and heifers that were purchased after initiation of the study and not enrolled in the study were vaccinated by the herd manager with the Salmonella Vetovax™ SRP® vaccine

Overview of the results

  • Both vaccinates and controls showed decreased Salmonella fecal shedding
  • Decreased somatic cell count (SCC) in vaccinates vs. controls
    • 179,000 vs 439,000 at 30-60 days in milk (DIM) (P<0.01)
  • Mean parity adjusted average daily milk yield was greater in vaccinates
    • Additional 1.14 kg/cow/day in the first 90 DIM (P<0.01)
  • Vaccinated cattle had higher concentrations of circulating antibodies at both samplings: 7-14 and 28-35 DIM (P=0.01)

General conclusions

Vaccinating dairy cows with Salmonella Vetovax™ SRP® resulted in higher adjusted average daily milk yield (+1.14 kg), a decrease in SCC, and a significant increase in circulating antibodies. Since Salmonella bacteria are present on most dairy operations, this serologic response is positive. Vaccination with Salmonella Vetovax™ SRP® resulted in a significant increase in milk yield which may lead to improved profitability for dairy operators.

Salmonella Vetovax™ SRP® — a new vaccine using the innovative SRP® technology helping to prevent Salmonella Newport infections, reduce fecal shedding, and increase milk production in the context of subclinical Salmonella infections — is now available from Vetoquinol.

The Salmonella Vetovax™ SRP® vaccine represents an effective strategy to control Salmonella Newport outbreaks in dairy operations and a great way to keep milk production flowing.

Effect of Salmonella SRP vaccination
on milk production

‌‌+ 1.14 kg


Cows administered SRP vaccine showed a 1.14 kg increase in milk production per day.
Source: Kansas State University study

Effect of Salmonella SRP vaccination
on somatic cell count (SCC) (cells/mL)



From 30 to 60 days after calving, SRP vaccinates had a significantly lower somatic cell count.
Source: Kansas State University study
Source for the data provided here
HERMESCH, D.R., THOMSON, D.U., LONERAGAN, G.H.,RENTER, D.R., WHITE, B.J. (Sept. 2008). Effects of a commercially available vaccine against Salmonella enterica serotype Newport on milk production, somatic cell count, and shedding of Salmonella organisms in female dairy cattle with no clinical signs of salmonellosis, AJVR, 69(9): 1229-1234.