Objective—To evaluate antimicrobial susceptibility of commensal Escherichia coli strains isolated from the feces of horses and investigate relationships with hospitalization and antimicrobial drug (AMD) administration.
Animals—68 hospitalized horses that had been treated with AMDs for at least 3 days (HOSP–AMD group), 63 hospitalized horses that had not received AMDs for at least 4 days (HOSP–NOAMD group), and 85 healthy horses that had not been hospitalized or treated with AMDs (community group).
Procedures—Fecal samples were submitted for bacterial culture, and up to 3 E coli colonies were recovered from each sample. Antimicrobial susceptibility of 724 isolates was evaluated. Prevalence of resistance was compared among groups by use of log-linear modeling.
Results—For 12 of the 15 AMDs evaluated, prevalence of antimicrobial resistance differed significantly among groups, with prevalence being highest among isolates from the HOSP–AMD group and lowest among isolates from the community group. Isolates recovered from the HOSP–AMD and HOSP–NOAMD groups were also significantly more likely to be resistant to multiple AMDs. Resistance to sulfamethoxazole and resistance to trimethoprim-sulfamethoxazole were most common, followed by resistance to gentamicin and resistance to tetracycline. Use of a potentiated sulfonamide, aminoglycosides, cephalosporins, or metronidazole was positively associated with resistance to 1 or more AMDs, but use of penicillins was not associated with increased risk of resistance to AMDs.
Conclusion and Clinical Relevance—Results suggest that both hospitalization and AMD administration were associated with prevalence of antimicrobial resistance among E coli strains isolated from the feces of horses.
Objective—To evaluate trends in feedlot cattle mortality
ratios over time, by primary body system affected,
and by type of animal.
Design—Retrospective cohort study.
Animals—Approximately 21.8 million cattle entering
121 feedlots in the United States during 1994 through
Procedures—Yearly and monthly mortality ratios
were calculated. Numbers of deaths were modeled
by use of Poisson regression methods for repeated
measures. Relative risks of death over time and by
animal type were estimated.
Results—Averaged over time, the mortality ratio
was 12.6 deaths/1,000 cattle entering the feedlots.
The mortality ratio increased from 10.3
deaths/1,000 cattle in 1994 to 14.2 deaths/1,000
cattle in 1999, but this difference was not statistically
significant (P = 0.09). Cattle entering the feedlots
during 1999 had a significantly increased risk
(relative risk, 1.46) of dying of respiratory tract disorders,
compared with cattle that entered during
1994, and respiratory tract disorders accounted for
57.1% of all deaths. Dairy cattle had a significantly
increased risk of death of any cause, compared with
beef steers. Beef heifers had a significantly
increased risk of dying of respiratory tract disorders,
compared with beef steers.
Conclusions and Clinical Relevance—Results suggested
that although overall yearly mortality ratio did
not significantly increase during the study, the risk of
death attributable to respiratory tract disorders was
increased during most years, compared with risk of
death during 1994. The increased rates of fatal respiratory
tract disorders may also reflect increased rates
of non-fatal respiratory tract disorders, which would
be expected to have adverse production effects in
surviving animals. (J Am Vet Med Assoc 2001;219:1122–1127)
Objective—To evaluate biosecurity practices of cowcalf
Sample Population—2,713 cow-calf operations
were used in phase 1 of the study, and 1,190 cow-calf
operations were used in phase 2.
Procedure—Producers were contacted for a personal
interview between Dec 30, 1996 and Feb 3, 1997
regarding their management practices. Noninstitutional
operations with 1 or more beef cows were
eligible to participate in the study. Producers who participated
in the first phase of the study and who had
≥ 5 beef cows were requested to continue in the
study and were contacted by a veterinarian or animal
health technician who administered further questionnaires.
All contacts for the second phase of the study
were made between Mar 3, 1997 and Apr 30, 1997.
Additional data on use of various vaccines, testing of
imported cattle for brucellosis, Mycobacterium
paratuberculosis, bovine viral diarrhea, and tuberculosis
as well as potential for feed contamination were
collected during the second phase of the study.
Results—Producers commonly engaged in management
practices that increased risk of introducing disease
to their cattle such as importing cattle, failing to
quarantine imported cattle, and communal grazing.
Producers inconsistently adjusted for the increased risk
of their management practices by increasing the types
of vaccines given, increasing the quarantine time or
proportion of imported animals quarantined, or increasing
testing for various diseases in imported animals.
Conclusions and Clinical Relevance—Cow-calf
herds are at risk for disease exposure from outside
sources when cattle are introduced to the herd, and
producers do not always adjust management practices
such as vaccination schedules and quarantine
procedures appropriately to minimize this risk.
Veterinary involvement in education of producers
regarding biosecurity risks and development of rational
and economical biosecurity plans is needed. (J Am
Vet Med Assoc 2000;217:185–189)
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)
Objective—To determine current practices regarding
use of antimicrobials in equine patients undergoing
surgery because of colic at veterinary teaching hospitals.
Sample Population—Diplomates of the American
College of Veterinary Surgeons performing equine
surgery at veterinary teaching hospitals in the United
Procedure—A Web-based questionnaire was developed,
and 85 surgeons were asked to participate. The
first part of the survey requested demographic information
and information about total number of colic
surgeries performed at the hospital, number of colic
surgeries performed by the respondent, and whether
the hospital had written guidelines for antimicrobial
drug use. The second part pertained to nosocomial
infections. The third part provided several case scenarios
and asked respondents whether they would
use antimicrobial drugs in these instances.
Results—Thirty-four (40%) surgeons responded to
the questionnaire. Respondents indicated that most
equine patients undergoing surgery because of colic
at veterinary teaching hospitals in the United States
received antimicrobial drugs. Drugs that were used
were similar for the various hospitals that were represented,
and for the most part, the drugs that were
used were fairly uniform irrespective of the type of
colic, whereas the duration of treatment varied with
the type of colic and the surgical findings. The combination
of potassium penicillin and gentamicin was the
most commonly used treatment.
Conclusions and Clinical Relevance—Results of
this study document the implementation of recommendations
by several authors in veterinary texts that
antimicrobial drugs be administered perioperatively in
equine patients with colic that are undergoing surgery.
However, the need for long-term antimicrobial drug
treatment in equine patients with colic is unknown. (J
Am Vet Med Assoc 2002;220:1359–1365)
Objective—To assess associations between herd management practices and herd-level rates of bovine respiratory disease complex (BRDC) in preweaned beef calves in US cow-calf operations.
Sample—443 herds weighted to represent the US cow-calf population.
Procedures—Producers from 24 states were selected to participate in a 2-phase survey; 443 producers completed both survey phases and had calves born alive during the study period. Data from those respondents underwent multivariable negative binomial regression analyses.
Results—Bred heifer importation was associated with lower BRDC rates (incidence rate ratio [IRR], 0.40; confidence interval [CI], 0.19 to 0.82), whereas weaned steer importation was associated with higher BRDC rates (IRR, 2.62; CI, 1.15 to 5.97). Compared with single-breed herds, operations with calves of 2-breed crosses (IRR, 2.36; CI, 1.30 to 4.29) or 3-breed crosses (IRR, 4.00; CI, 1.93 to 8.31) or composite-herd calves (IRR, 2.27; CI, 1.00 to 5.16) had higher BRDC rates. Operations classified as supplemental sources of income had lower BRDC rates (IRR, 0.48; CI, 0.26 to 0.87) than did operations classified as primary sources of income. Reported feed supplementation with antimicrobials was positively associated with BRDC rates (IRR, 3.46; CI, 1.39 to 8.60). The reported number of visits by outsiders in an average month also was significantly associated with herd-level BRDC rates, but the magnitude and direction of the effects varied.
Conclusions and Clinical Relevance—Management practices associated with preweaning BRDC rates may be potential indicators or predictors of preweaning BRDC rates in cow-calf production systems.
Objective—To analyze the sulfur content of water
and forage samples from a geographically diverse
sample of beef cow-calf operations in the United
States and to estimate frequency and distribution of
premises where forage and water resources could
result in consumption of hazardous amounts of sulfur
Sample Population—709 forage samples from 678
beef cow-calf operations and individual water samples
from 498 operations in 23 states.
Procedure—Sulfur content of forage samples and
sulfate concentration of water samples were measured.
Total sulfur intake was estimated for pairs of
forage and water samples.
Results—Total sulfur intake was estimated for 454
pairs of forage and water samples. In general, highest
forage sulfur contents did not coincide with highest
water sulfate concentrations. Overall, 52 of the 454
(11.5%) sample pairs were estimated to yield total
sulfur intake (as a percentage of dry matter) ≥ 0.4%,
assuming water intake during conditions of high
ambient temperature. Most of these premises were
in north-central (n = 19) or western (19) states.
Conclusions and Clinical Relevance—Results suggest
that on numerous beef cow-calf operations
throughout the United States, consumption of forage
and water could result in excessively high sulfur
intake. All water sources and dietary components
should be evaluated when assessing total sulfur
intake. Knowledge of total sulfur intake may be useful
in reducing the risk of sulfur-associated health and
performance problems in beef cattle. (J Am Vet Med Assoc
OBJECTIVE To identify geographic areas in the United States where food animal veterinary services may be insufficient to meet increased needs associated with the US FDA's Veterinary Feed Directive.
DESIGN Cross-sectional study.
SAMPLE Data collected between 2010 and 2016 from the US Veterinary Medicine Loan Repayment Program, the National Animal Health Monitoring System Small-Scale US Livestock Operations Study, and the USDA's National Veterinary Accreditation Program.
PROCEDURES Each dataset was analyzed separately to identify geographic areas with greatest potential for veterinary shortages. Geographic information systems methods were used to identify co-occurrence among the datasets of counties with veterinary shortages.
RESULTS Analysis of the loan repayment program, Small-Scale Livestock Operations Study, and veterinary accreditation datasets revealed veterinary shortages in 314, 346, and 117 counties, respectively. Of the 3,140 counties in the United States during the study period, 728 (23.2%) counties were identified as veterinary shortage areas in at least 1 dataset. Specifically, 680 counties were identified as shortage areas in 1 dataset, 47 as shortage areas in 2 datasets, and 1 Arizona county as a shortage area in all 3 datasets. Arizona, Kentucky, Missouri, South Dakota, and Virginia had ≥ 3 counties identified as shortage areas in ≥ 2 datasets.
CONCLUSIONS AND CLINICAL RELEVANCE Many geographic areas were identified across the United States where food animal veterinary services may be inadequate to implement the Veterinary Feed Directive and meet other producer needs. This information can be used to assess the impact of federal regulations and programs and help understand the factors that influence access to food animal veterinary services in specific geographic areas.
Objective—To estimate the prevalence of
Mycobacterium avium subsp paratuberculosis infection
among cows on beef operations in the United
Design—Cross-sectional seroprevalence study.
Sample Population—A convenience sample of 380
herds in 21 states.
Procedure—Serum samples were obtained from
10,371 cows and tested for antibodies to M avium
subsp paratuberculosis with a commercial ELISA .
Producers were interviewed to collect data on herd
Results—30 (7.9%) herds had 1 or more animals for
which results of the ELISA were positive; 40 (0.4%)
of the individual cow samples yielded positive results.
None of the herd management practices studied
were found to be associated with whether any animals
in the herd would be positive for antibodies to M
avium subsp paratuberculosis.
Conclusions and Clinical Relevance—Results suggest
that the prevalence of antibodies to M avium
subsp paratuberculosis among beef cows in the
United States is low. Herds with seropositive animals
were widely distributed geographically. (J Am Vet
Med Assoc 2001;219:497–501)