Objective—To compare prevalence of tetracycline resistance genes in the fecal flora of conventionally raised feedlot steers and feedlot steers raised without antimicrobials.
Sample Population—61 fecal samples from conventionally raised steers and 61 fecal samples from steers raised without antimicrobials at a single feedlot.
Procedures—Total DNA was extracted from each fecal sample and analyzed by means of 4 multiplex PCR assays for 14 tetracycline resistance genes.
Results—At least 3 tetracycline resistance genes were identified in all 122 fecal samples. For 5 of the 14 tetracycline resistance genes, the percentage of samples in which the gene was detected was significantly higher for fecal samples from conventionally raised cattle than for fecal samples from antimicrobial-free cattle, and for 1 gene, the percent-age of samples in which the gene was detected was significantly higher for fecal samples from antimicrobial-free cattle than for fecal samples from conventionally raised cattle. The percentage of samples with r 11 tetracycline resistance genes was significantly higher for fecal samples from conventionally raised cattle (35/61 [57%]) than for fecal samples from antimicrobial-free cattle (16/61 [26%]).
Conclusions and Relevance—Results suggested that the prevalence of tetracycline resistance genes was significantly higher in the fecal flora of conventionally raised feedlot steers than in the fecal flora of feedlot steers raised without antimicrobials and that a metagenomic approach may be useful in understanding the epidemiology of antimicrobial resistance in food animals.
Objective—To estimate prevalence of Salmonella
spp in Ohio dairy farms and to identify potential risk
factors for fecal shedding of salmonellae.
Sample Population—105 Ohio dairy farms.
Procedure—Individual fecal samples from all mature
cows in study herds were tested for Salmonella spp
by use of standard bacteriologic culture procedures.
Herds were identified as infected if at least 1 cow
was shedding Salmonella spp. Information regarding
herd characteristics, management practices, and
health history were collected. Potential risk factors for
herd-level Salmonella infection were identified.
Results—In 31% of the study herds (95% confidence
interval, 22 to 40%), at least 1 cow was shedding
Salmonella spp. Six percent of 7,776 fecal samples
contained Salmonella organisms; prevalence within
infected herds ranged from < 1 to 97%. Herd size,
use of free stalls for lactating and nonlactating cows,
and use of straw bedding in nonlactating cows were
significantly associated with fecal shedding of
Salmonella spp, as determined by use of univariate
analysis . By use of multivariate analysis, large herds
were more likely to be infected than smaller herds;
however, no other factors were associated with
Salmonella infection after adjustment for herd size.
Conclusions and Clinical Relevance—Subclinical
shedding of Salmonella spp is common in Ohio dairy
herds, although we could not identify specific interventions
that may influence the prevalence of
Salmonella spp on dairy farms. It appears that large
herd size and intensive management may provide an
environment conducive to Salmonella shedding and
chronic dairy herd infection. (J Am Vet Med Assoc
Objective—To evaluate various sampling strategies for potential use in measuring prevalence of antimicrobial susceptibility in cattle.
Sample Population—500 isolates of non–type-specific Escherichia coli (NTSEC) isolated from the feces of 50 cows from 2 dairy farms (25 cows/farm and 10 isolates/cow).
Procedures—Diameters of inhibition zones for 12 antimicrobials were analyzed to estimate variation among isolates, cows, and farms and then used to determine sampling distributions for a stochastic simulation model to evaluate 4 sampling strategies. These theoretic sampling strategies used a total of 100 isolates in 4 allocations (1 isolate from 100 cows, 2 isolates from 50 cows, 3 isolates from 33 cows, or 4 isolates from 25 cows).
Results—Analysis of variance composition revealed that 74.2% of variation was attributable to isolates, 18.5% to cows, and 7.3% to farms. Analysis of results of simulations suggested that when most of the variance was attributable to differences among isolates within a cow, culturing 1 isolate from each of 100 cows underestimated overall prevalence, compared with results for culturing more isolates per cow from fewer cows. When variance was not primarily attributable to differences among isolates, all 4 sampling strategies yielded similar results.
Conclusions and Clinical Relevance—It is not always possible to predict the hierarchical level at which clustering will have its greatest impact on observed susceptibility distributions. Results suggested that sampling strategies that use testing of 3 or 4 isolates/cow from a representative sample of all animals better characterize herd prevalence of antimicrobial resistance when impacted by clustering.
Objective–To determine prevalence of pain among
dogs and cats examined as outpatients at a veterinary
teaching hospital and characteristics of pain in dogs
and cats with evidence of pain.
Animals–1,153 dogs and 652 cats examined as outpatients
at The Ohio State University during 2002.
Procedure–A questionnaire was administered to
owners of all dogs and cats. For dogs and cats with
evidence of pain, the cause, signs, anatomic location,
type (superficial somatic, deep somatic, or visceral),
duration, and severity of the pain and the principle
mechanism (inflammatory, neuropathic, both, or
unknown) responsible for the pain were determined
on the basis of questionnaire responses and results
of physical examination. The presence of primary
hyperalgesia, secondary hyperalgesia, allodynia, and
hyposensitivity was recorded.
Results–231 (20%) dogs and 92 (14%) cats had evidence
of pain. Dogs with evidence of pain were significantly
older and heavier than dogs without. Cats
with evidence of pain were significantly older than
cats without. In most dogs and cats with evidence of
pain, the pain was determined to be of short duration
(< 7 days), of mild or moderate severity, somatic,
associated with primary hyperalgesia, and inflammatory.
Analgesic drugs were frequently administered to
dogs with chronic pain, but were not always considered
Conclusions and Clinical Relevance–Results suggest
that mild or moderate pain associated with
inflammation may be seen in dogs and cats examined
as outpatients. Older, heavier dogs and older cats
were more likely to have evidence of pain. (J Am Vet
Med Assoc 2004;224:1459–1463)
Objective—To monitor patterns of Salmonella fecal
shedding in naturally infected dairy herds, determine
the association between fecal shedding and individual
animal production measures, and evaluate potential
risk factors for shedding of Salmonella organisms
among cattle in dairy herds.
Sample Population—5 Ohio dairy herds.
Procedure—For 3 herds, fecal samples were collected
from all mature cows and unweaned calves 7
times during an 18-month period. For the remaining 2
herds, fecal samples were collected from 50 lactating
cows 6 times during a 12-month period. Individual
animal production records for 3 herds were used to
examine associations between individual fecal
Salmonella shedding status and 305-day matureequivalent
milk production, somatic cell count, milk
fat content, and milk protein content. Multivariable
logistic regression was used to test for associations
between fecal shedding status and breed, lactation
status, lactation number, and duration of lactation.
Results—None of the adult animals had clinical signs
of salmonellosis, but prevalence of fecal Salmonella
shedding at individual collection times ranged from 0
to 99% for cows and from 0 to 67% for unweaned
calves. Mature cows were more likely to be shedding
Salmonella organisms than were unweaned calves.
Within herds, lactation status and duration of lactation
for individual animals were associated with
Salmonella shedding status. Salmonella fecal shedding
status was not associated with individual cow
Conclusions and Clinical Relevance—Results suggest
that subclinical fecal Salmonella shedding can
persist in dairy herds for up to 18 months with no
measurable effects on health or production of individual
cows. (J Am Vet Med Assoc 2002;220:650–655)
Objective—To determine whether bulk-tank standard
plate counts or plate loop counts and bulk-tank
somatic cell counts (SCC) were associated with
detection of violative antimicrobial residues in milk
from dairy cattle.
Procedure—Information for 1994 through 1997 was
obtained from a large milk marketing cooperative that
operated in multiple states throughout the northeastern
and midwestern United States (16,831 herd-years
of information from 6,546 farms) and from the Ohio
Department of Agriculture Grade-A Milk Certification
Program (12,042 herd-years of information from 4,022
farms). Data were analyzed by use of multivariate
Results—For both data sets, odds that a violative
antibiotic residue would be detected increased as
mean SCC for the herd-year increased. Standard plate
counts and plate loop counts were not associated
with odds that a violative antibiotic residue would be
Conclusions and Clinical Relevance—Results of
this study suggested that the odds that a violative
antibiotic residue would be found in bulk-tank milk
increased as mean SCC for the herd-year increased.
This suggests that management practices that would
be expected to influence SCC may also influence the
risk of antibiotic residue violations. (J Am Vet Med
Objective—To estimate the prevalence and characteristics
of pain in dogs and cats examined by an
emergency service at a veterinary teaching hospital
and evaluate the response of dogs and cats with
signs of pain to analgesic treatment.
Animals—317 dogs and 112 cats.
Procedure—A questionnaire was used to categorize
the characteristics of pain. The location, cause, and
signs of pain were determined by obtaining a thorough
history and conducting a physical examination.
Pain was categorized by type (superficial somatic,
deep somatic, or visceral), mechanism (inflammatory,
neuropathic, or both), severity (mild, moderate, or
severe), and duration. Evidence for primary or secondary
hypersensitivity and hyposensitivity to manipulation
was determined. The response to single or
multiple analgesic drug administration was assessed.
Results—179 (56%) dogs and 60 (54%) cats had
signs of pain. In most of these dogs and cats, pain
was classified as acute (< 24 hours' duration) and of
moderate severity and was associated with primary
hypersensitivity. Most dogs had deep somatic pain;
most cats had visceral pain. Inflammation was the
most common mechanism. One hundred nineteen
(66%) dogs and 41 (68%) cats were treated with analgesic
drugs. Analgesic treatment was considered
effective in 73 (61%) dogs and 31 (76%) cats.
Conclusions and Clinical Relevance—Results suggest
that moderate to severe acute somatic pain
caused by inflammation is common in dogs and cats
examined by an emergency service and that a combination
of multiple analgesic drugs is more effective
than any single analgesic drug in the treatment of pain
in these dogs and cats. (J Am Vet Med Assoc 2005;226:2004–2009)
Objective—To compare shedding patterns and serologic responses to bovine coronavirus (BCV) in feedlot calves shipped from a single ranch in New Mexico (NM calves) versus calves assembled from local sale barns in Arkansas (AR calves) and to evaluate the role of BCV on disease and performance.
Animals—103 feedlot calves from New Mexico and 100 from Arkansas.
Procedures—Calves were studied from before shipping to 35 days after arrival at the feedlot. Nasal swab specimens, fecal samples, and serum samples were obtained before shipping, at arrival, and periodically thereafter. Bovine coronavirus antigen and antibodies were detected by use of an ELISA.
Results—NM calves had a high geometric mean titer for BCV antibody at arrival (GMT, 1,928); only 2% shed BCV in nasal secretions and 1% in feces. In contrast, AR calves had low antibody titers against BCV at arrival (GMT, 102) and 64% shed BCV in nasal secretions and 65% in feces. Detection of BCV in nasal secretions preceded detection in feces before shipping AR calves, but at arrival, 73% of AR calves were shedding BCV in nasal secretions and feces. Bovine coronavirus infection was significantly associated with respiratory tract disease and decreased growth performance in AR calves.
Conclusions and Clinical Relevance—Replication and shedding of BCV may start in the upper respiratory tract and spread to the gastrointestinal tract. Vaccination of calves against BCV before shipping to feedlots may provide protection against BCV infection and its effects with other pathogens in the induction of respiratory tract disease.
Objective—To determine the prevalence, fecal shedding
pattern, and association of bovine torovirus
(BoTV) with diarrhea in veal calves at time of arrival
and periodically throughout the first 35 days after their
arrival on a veal farm.
Animals—62 veal calves.
Procedure—Fecal samples collected on days 0, 4, 14,
and 35 after arrival were tested for BoTV by use of
ELISA and reverse transcriptase-polymerase chain
reaction (RT-PCR) assay. Paired serum samples
obtained from blood collected on days 0 and 35 were
analyzed for BoTV antibodies with a hemagglutination
inhibition assay. Fecal samples were also screened
for other enteric pathogens, including rotavirus, coronavirus,
and Cryptosporidium spp.
Results—Fecal shedding of BoTV was detected in 15
of 62 (24%) calves by use of ELISA and RT-PCR assay,
with peak shedding on day 4. A significant independent
association between BoTV shedding and diarrhea
was observed. In addition, calves shedding ≥ 2
enteric pathogens were more likely to have diarrhea
than calves shedding ≤ 1 pathogen. Calves that were
seronegative or had low antibody titers against BoTV
(≤ 1:10 hemagglutination inhibition units) at arrival
seroconverted to BoTV (> 4-fold increase in titer);
these calves were more likely to shed virus than
calves that were seropositive against BoTV at arrival.
Conclusions and Clinical Relevance—Shedding of
BoTV was strongly associated with diarrhea in neonatal
veal calves during the first week after arrival at the
farm. These data provide evidence that BoTV is an
important pathogen of neonatal veal calves.
(Am J Vet Res 2003;64:485–490)
Objective—To evaluate the effectiveness of various
sampling techniques for determining antimicrobial
resistance patterns in Escherichia coli isolated from
feces of feedlot cattle.
Sample Population—Fecal samples obtained from
328 beef steers and 6 feedlot pens in which the cattle
Procedure—Single fecal samples were collected
from the rectum of each steer and from floors of pens
in which the cattle resided. Fecal material from each
single sample was combined into pools containing 5
and 10 samples. Five isolates of Escherichia coli from
each single sample and each pooled sample were
tested for susceptibility to 17 antimicrobials.
Results—Patterns of antimicrobial resistance for
fecal samples obtained from the rectum of cattle did
not differ from fecal samples obtained from pen
floors. Resistance patterns from pooled samples differed
from patterns observed for single fecal samples.
Little pen-to-pen variation in resistance prevalence
was observed. Clustering of resistance phenotypes
within samples was detected.
Conclusions and Clinical Relevance—Studies of
antimicrobial resistance in feedlot cattle can rely on
fecal samples obtained from pen floors, thus avoiding
the cost and effort of obtaining fecal samples from the
rectum of cattle. Pooled fecal samples yielded resistance
patterns that were consistent with those of single
fecal samples when the prevalence of resistance
to an antimicrobial was > 2%. Pooling may be a practical
alternative when investigating patterns of resistance
that are not rare. Apparent clustering of resistance
phenotypes within samples argues for examining
fewer isolates per fecal sample and more fecal
samples per pen. (Am J Vet Res 2002;63:1662–1670)