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 whether a combination viral vaccine containing a modified-live bovine herpesvirus-1 (BHV-1) would protect calves from infection with virulent field strains of BHV-1 for weeks or months after vaccination.
Design—Randomized controlled trial, performed in 2 replicates.
Animals—63 weaned 4- to 6-month-old crossbred beef calves seronegative for antibody against BHV-1.
Procedures—Calves were randomly allocated to 1 of 2 treatment groups. Control calves (n = 10/replicate) received a combination modified-live mixed viral vaccine without BHV-1, and treatment calves (20 and 23/replicate) received a combination modified-live mixed viral vaccine containing BHV-1. Each group was challenged via aerosol with 1 of 2 field strains of BHV-1, 30 days after vaccination in replicate 1 and 97 days after vaccination in replicate 2. After challenge, calves were commingled in 1 drylot pen. Clinical signs, immune responses, and nasal shedding of virus were monitored for 10 days after challenge, after which the calves were euthanatized and tracheal lesions were assessed.
Results—Vaccination stimulated production of BHV-1–specific IgG antibody that cross-neutralized several field and laboratory strains of BHV-1. Challenge with both field strains of BHV-1 resulted in moderate to severe respiratory tract disease in control calves. Treatment calves had significantly fewer signs of clinical disease, shed less BHV-1, had less or no weight loss after challenge, and had fewer tracheal lesions than control calves for at least 97 days after vaccination.
Conclusions and Clinical Relevance—Administration of the combination modified-live BHV-1 vaccine yielded significant disease-sparing effects in calves experimentally infected with virulent field strains of BHV-1.
Objective—To compare the frequency of isolation,
genotypes, and in vivo production of major lethal toxins
of Clostridium perfringens in adult dairy cows
affected with hemorrhagic bowel syndrome (HBS)
versus left-displaced abomasum (LDA).
Animals—10 adult dairy cattle with HBS (cases) and
10 adult dairy cattle with LDA matched with cases by
herd of origin (controls).
Procedure—Samples of gastrointestinal contents
were obtained from multiple sites during surgery or
necropsy examination. Each sample underwent testing
for anaerobic bacteria by use of 3 culture methods.
The genotype of isolates of C perfringens was
determined via multiplex polymerase chain reaction
assay. Major lethal toxins were detected by use of an
ELISA. Data were analyzed with multivariable logistic
regression and X2 analysis.
Results—C perfringens type A and type A with the
beta2 gene (A + beta2) were the only genotypes isolated.
Isolation of C perfringens type A and type A +
beta2 was 6.56 and 3.3 times as likely, respectively,
to occur in samples from cattle with HBS than in cattle
with LDA. Alpha toxin was detected in 7 of 36
samples from cases and in 0 of 32 samples from controls.
Beta2 toxin was detected in 9 of 36 samples
from cases and 0 of 36 samples from controls.
Conclusions and Clinical Relevance—C perfringens
type A and type A + beta2 can be isolated from the gastrointestinal
tract with significantly greater odds in cattle
with HBS than in herdmates with LDA. Alpha and beta2
toxins were detected in samples from cows with HBS
but not from cows with LDA. (J Am Vet Med Assoc 2005;227:132–138)
Objective—To determine the percentage of broodmares
and foals that shed Clostridium perfringens in
their feces and classify the genotypes of those isolates.
Design—Prospective cross-sectional study.
Animals—128 broodmares and their foals on 6
Procedures—Anaerobic and aerobic bacteriologic
cultures were performed on feces collected 3 times
from broodmares and foals. All isolates of C perfringens
Results—Clostridium perfringens was isolated from
the feces of 90% of 3-day-old foals and 64% of foals
at 8 to 12 hours of age. A lower percentage of broodmares
and 1- to 2-month-old foals shed C perfringens
in their feces, compared with neonatal foals. Among
samples with positive results, C perfringens type A
was the most common genotype identified (85%); C
perfringens type A with the β2 toxin gene was identified
in 12% of samples, C perfringens type A with the
enterotoxin gene was identified in 2.1% of samples,
and C perfringens type C was identified in < 1% of
Conclusions and Clinical Relevance—Clostridium
perfringens was identified from the feces of all but 6
foals by 3 days of age and is likely part of the normal
microflora of neonatal foals. Most isolates from
broodmares and foals are C perfringens type A; thus,
the clinical relevance of culture results alone is questionable.
Clostridium perfringens type C, which has
been associated with neonatal enterocolitis, is rarely
found in the feces of horses. (J Am Vet Med Assoc