Objective—To evaluate the ability of orally administered
aspirin to mitigate 3-methylindole (3MI)-induced
respiratory tract disease and reduced rate of gain in
Animals—244 beef cattle.
Procedure—In a masked, randomized, controlled
field trial, calves were untreated (controls) or received
a single orally administered dose of aspirin (31.2 g) on
entry into a feedlot. Serum 3MI concentrations were
measured on days 0, 3, and 6. Rumen 3MI concentration
was measured on day 3. Cattle were observed
daily for clinical signs of respiratory tract disease.
Lungs were evaluated at slaughter for gross pulmonary
Results—Mean daily gain (MDG) in cattle treated
with aspirin, compared with control cattle, was 0.06
kg greater in the backgrounding unit and 0.03 kg
greater for the overall feeding period. Neither serum
nor rumen 3MI concentrations appeared to modify
this effect. Cattle treated with aspirin were more likely
to be treated for respiratory tract disease.
Mortality rate, gross pulmonary lesions, and serum
and rumen 3MI concentrations were similar between
groups. Increased rumen 3MI concentration was
associated with a small difference in risk of lung
Conclusions and Clinical Relevance—Cattle given a
single orally administered dose of aspirin on feedlot
entry had higher MDG in the backgrounding unit and
for the overall feeding period, but this finding could
not be attributed to mitigation of effects of 3MI. This
may have been influenced by low peak 3MI production
and slow rates of gain. (Am J Vet Res
Objective—To determine whether immunity against
bovine respiratory syncytial virus (BRSV) mitigates the
effects of 3-methylindole (3MI) on occurrence of
bovine respiratory tract disease (BRD) and rate of gain
in feedlot cattle.
Animals—254 mixed-breed beef cattle.
Procedure—Cattle were randomly assigned to 1 of 3
groups at the time of arrival at the feedlot. One group
was vaccinated with an inactivated BRSV vaccine,
another was vaccinated with a modified-live BRSV
vaccine, and the third was maintained as unvaccinated
control cattle. On days 0 and 28, serum BRSV antibody
concentrations were measured, using serum
neutralizing and ELISA techniques. Serum 3MI concentrations
were measured at feedlot arrival and 3
days later. Cattle were monitored for development of
BRD. At slaughter, lungs were evaluated grossly for
Results—Higher serum 3MI concentrations early in
the feeding period were associated with lower mean
daily gain. Control cattle were more likely to be treated
for BRD after day 3, compared with cattle vaccinated
with the modified-live BRSV vaccine. Humoral immunity
against BRSV did not appear to modify the effect of
3MI on development of BRD or mean daily gain.
Conclusions and Clinical Relevance—Results suggest
that abrogating the effects of 3MI and BRSV
infection may improve the health and growth performance
of feedlot cattle. However, in this study, immunity
against BRSV did not appear to protect against
the potential synergism between 3MI and BRSV
infection, possibly because of the slow rates of gain
of cattle included in the study or timing of sample collection.
(Am J Vet Res 2000;61:1309–1314)
Objective—To determine the association between
respiratory tract infection with bovine coronavirus
(BCV), treatment for respiratory tract disease, pulmonary
lesions at slaughter, and average daily gain in
cattle in feedlots.
Animals—837 calves in feedlots in Ohio and Texas.
Procedure—Nasal swab specimens were obtained
from cattle at arrival in a feedlot (day 0) and at various
times during the initial 28 days after arrival.
Specimens were tested for BCV, using an antigencapture
ELISA. Serum samples were obtained at
arrival and again 28 days after arrival and tested for
antibodies to BCV, using an antibody-detection ELISA.
Information was collected regarding treatment for
cattle with respiratory tract disease and average daily
gain during the feeding period. Pulmonary lesions
were evaluated at slaughter.
Results—Cattle shedding BCV from the nasal cavity
and developing an antibody response against BCV
were 1.6 times more likely to require treatment for
respiratory tract disease than cattle that did not shed
the virus or develop an immune response against
BCV. Additionally, cattle that shed BCV from the nasal
cavity were 2.2 times more likely to have pulmonary
lesions at slaughter than cattle that did not shed the
virus. The BCV shedding or seroconversion status did
not affect average daily gain.
Conclusions and Clinical Relevance—Bovine coronavirus
infects feedlot cattle and is associated with an
increased risk for cattle developing respiratory tract
disease and pulmonary lesions. Development of
appropriate control measures could help reduce the
incidence of respiratory tract disease. (Am J Vet Res