Objective—To evaluate the health and performance
of young dairy calves vaccinated with a commercial
Mannheimia haemolytica and Pasteurella multocida
Design—Randomized clinical trial.
Animals—358 Holstein dairy calves between 14 and
20 days of age on 8 farms.
Procedure—Calves were randomly assigned to a
control or vaccinated group. The vaccine used was a
commercial modified-live M haemolytica and P multocida
vaccine that was administered on days 0 and
14. Calf weight was measured on day 0 and monthly
for 3 months. Farmers were asked to record any treatment
given to the calves and the reason for treatment
during the 4 months of the study. Blood was collected
from all calves on days 0 and 28, and titers of antibodies
to M haemolyticawere determined by means
of direct bacterial agglutination.
Results—Mean daily gain was not significantly different
between vaccinated and control calves. Vaccinated
calves had a significantly greater increase in antibody
titers (5.3-fold increase), compared with control calves
(3.6-fold increase). There was no significant difference
between vaccinated and control calves for any of the
treatment outcomes (number and duration of treatments
and age at first and last treatments).
Conclusions and Clinical Relevance—Results suggest
that the M haemolytica and P multocidavaccine,
given twice 2 weeks apart, was effective in increasing
titers of antibodies against M haemolytica in young
dairy calves but did not improve calf performance or health. (J Am Vet Med Assoc 2001;219:1739–1742)