Objective—To determine the effects of 2 anti-inflammatory
drugs in lactating Holstein cows with endotoxin-
Animals—30 multiparous Holstein cows that had
been lactating for 30 to 60 days.
Procedure—Bacterial culture of milk samples and
physical examinations established that study cows
were in good health and free of mastitis. Mastitis was
induced in 1 front mammary gland by intramammary
administration of purified bacterial endotoxin. Cows
were allocated into 1 of 3 treatment groups: untreated
endotoxic mastitis (n = 9), endotoxic mastitis plus
flunixin meglumine (9), and endotoxic mastitis plus
isoflupredone acetate (10). Heart rate, rectal temperature,
mammary surface area, and rumen motility
were recorded hourly for 14 hours following endotoxin
administration. Flunixin meglumine or isoflupredone
acetate was administered after mammary
swelling and rectal temperature ≥ 40°C had developed.
Milk production was evaluated from 5 days
before to 10 days after induction of mastitis.
Results—Neither drug ameliorated loss of milk production
or swelling of the affected mammary gland.
Both drugs reduced mean heart rate during the 14
hours following endotoxin administration, compared
with untreated control cows. Cows treated with flunixin
meglumine had increased rumen motility and
decreased rectal temperature during the same period,
compared with all other cows.
Conclusions and Clinical Relevance—Neither drug
enhanced recovery of milk production following endotoxin-
induced mastitis. Flunixin meglumine decreased
rectal temperature, whereas isoflupredone did not;
however, it has not been established that reduction of
fever is beneficial to cows with naturally occurring
mastitis. ( Am J Vet Res 2004;65:64–68)
Objective—To determine the association between
the existence of a calf persistently infected (PI) with
bovine viral diarrhea virus (BVDV) and pen morbidity.
Animals—5,041 calves in 50 pens at a feedlot in
Procedure—In a longitudinal study, ear notches were
collected from cattle and tested for BVDV antigen.
Characteristics of each pen (owner, sex, disease rate,
number of groups, and source) were recorded. The
association between the existence of a BVDV–PI calf
and morbidity in each pen was examined.
Results—Commingling was associated with an
increase in respiratory tract disease (odds ratio [OR],
3; 95% confidence interval [CI], 2.5 to 3.6). Ten
BVDV–PI calves (10/5,041 [0.2%]) were identified in 8
of 50 pens. A BVDV–PI calf was associated with
reduced pen-level respiratory tract disease (OR, 0.7;
95% CI, 0.5 to 0.9). Disease prevalence (mean ± SD
morbidity, 7.9 ± 3.1%) was lowest in pens containing
single-source cattle and a BVDV–PI calf (4 pens containing
302 cattle), compared with single-source cattle
with no BVDV–PI calf (mean morbidity, 11.89 ±
9.7%; 31 pens containing 3,093 cattle), commingled
cattle with no BVDV–PI calf (mean morbidity, 29.3 ±
16.22%; 11 pens containing 1,127 cattle), and commingled
cattle with a BVDV–PI calf (mean morbidity,
28.6 ± 10.1%; 4 pens containing 519 cattle).
Conclusions and Clinical Relevance—Commingling
was the greatest risk factor associated with morbidity
in each pen. A BVDV–PI calf in a pen was not associated
with increased disease prevalence in commingled
groups. (Am J Vet Res 2005;66:2130–2134)
Objective—To measure epithelial cell percentages and somatic cell counts (SCCs) in milk and determine whether isoflupredone acetate reduces mammary gland epithelial cell sloughing in cows with acute endotoxin-induced mastitis.
Animals—13 lactating Holstein cows.
Procedures—Determination of SCC and flow cytometric analysis of cytokeratin-positive (epithelial) cells in milk were performed before and 12 hours after induction of mastitis via intramammary administration of bacterial endotoxin in 8 cows and at the same time points in 5 cows without mastitis. Endotoxin-treated cows received isoflupredone acetate (20 mg) or saline (0.9% NaCl) solution (n = 4/group) IV after signs of mastitis developed.
Results—At the 12-hour time point, mean ± SD percentage of epithelial cells in milk increased from 2.74 ± 1.93% to 42.11 ± 36.21% and decreased from 5.73 ± 4.52% to 5.31 ± 1.93% in milk from cows with and without mastitis, respectively. Median (range) SCC in milk increased from 195,000 cells/mL (17,000 to 442,000 cells/mL) to 5,437,500 cells/mL (69,000 to 11,036,000 cells/mL) and from 19,000 cells/mL (9,000 to 125,000 cells/mL) to 51,000 cells/mL (10,000 to 835,000 cells/mL) in cows with and without mastitis, respectively. Changes in these variables were significantly greater in mastitis-affected cows. Administration of isoflupredone acetate did not affect epithelial cell percentage or SCC in milk.
Conclusions and Clinical Relevance—During the early phase of endotoxin-induced mastitis in dairy cows, large numbers of epithelial cells were sloughed into the milk. Epithelial cell damage likely precedes an influx of immune cells into affected mammary glands and may contribute to breakdown of the blood-milk barrier.
Objective—To determine the response of cortical bone to a multicomponent and nanostructural polymeric matrix as a drug delivery system for enhancing bone healing.
Animals—20 healthy adult crossbred goats.
Procedures—A 3.5-mm-diameter unicortical defect was created in each tibia (day 0), and goats (4 goats/group) were treated as follows: not treated (control group), grafted with the matrix, grafted with antimicrobial (tigecycline and tobramycin)–impregnated matrix, grafted with recombinant human bone morphogenetic protein type 2 (rhBMP-2)–impregnated matrix, or grafted with antimicrobial- and rhBMP-2–impregnated matrix. Elution kinetics of antimicrobials was monitored through plasma concentrations. Bone response was assessed with radiographic scoring (days 1 and 30) and dual-energy x-ray absorptiometry (days 1, 14, and 30). Goats were euthanized on day 30, and histomorphologic analysis was performed. Categorical variables were analyzed with a generalized linear model, and continuous variables were analyzed with an ANOVA.
Results—Plasma antimicrobial concentrations indicated continued release throughout the study. Radiography and dual-energy x-ray absorptiometry did not reveal significant differences among treatments on day 30. Periosteal reactions were significantly greater surrounding bone defects grafted with rhBMP-2–impregnated matrix than those not treated or grafted with matrix or with antimicrobial-impregnated matrix; periosteal reactions were similar in bone defects grafted with rhBMP-2–impregnated matrix and antimicrobial- and rhBMP-2–impregnated matrix.
Conclusions and Clinical Relevance—The matrix served as an antimicrobial delivery system and stimulated bone proliferation when rhBMP-2 was present. Antimicrobial and rhBMP-2 can be used concurrently, but the presence of antimicrobials may affect the performance of rhBMP-2.
Objective—To evaluate the impact of oxytetracycline exposure on horizontal transfer of an antimicrobial resistance plasmid.
Sample—Populations of Salmonella enterica subsp enterica serovar Typhimurium and Escherichia coli.
Procedures—Mixed populations of plasmid donor (Salmonella Typhimurium) and recipient (E coli) bacteria were assigned to 1 of 2 simulated oxytetracycline dosing regimens (high peak concentration-short elimination half-life [HC-SHL] or low peak concentration—long elimination half-life [LC-LHL]) or served as untreated control replicates. Donor, recipient, and transconjugant (E coli that acquired the plasmid) bacteria populations were quantified at 12, 24, and 36 hours after oxytetracycline administration by use of culture on selective bacterial growth media.
Results—The ratio of transconjugant to donor bacteria was significantly reduced in the oxytetracycline-exposed replicates, compared with the ratio for the control replicates, at 12 hours. At 24 and 36 hours, results for the HC-SHL regimens were not significantly different from results for the respective control replicates, and results for the LC-LHL regimens also were not significantly different from results for the respective control replicates. The oxytetracycline concentration at these time points (12 hours in the HC-SHL regimen and all 3 time points in the LC-LHL regimen) were in excess of the minimum inhibitory concentration of the recipient bacteria.
Conclusions and Clinical Relevance—Transfer of antimicrobial resistance plasmids may be suppressed in vitro by oxytetracycline exposure at concentrations greater than the minimum inhibitory concentration of the recipient bacteria.
Objective—To compare sensitivity of a complement fixation (CF) test and competitive ELISA (cELISA) for detection of Anaplasma marginale in experimentally infected steers.
Animals—40 crossbred (Angus-Simmental) steers.
Procedures—Steers were inoculated with 2.6 × 109A marginale–infected erythrocytes (day 0). Blood samples were collected on days 9, 13, 20, 28, 34, 41, 61, 96, 126, and 156 days after inoculation. The percentage of parasitized erythrocytes (PPE) was determined by microscopic examination of stained blood films, and sera were evaluated with the CF test and cELISA by use of USDA-approved methods. Sensitivity and agreement (κ statistic) between the 2 methods were determined. Persistent infections were confirmed by inoculation of blood obtained from infected steers into susceptible, splenectomized calves.
Results—9 days after inoculation, sensitivity of the cELISA was 47.5%, whereas the CF test failed to identify seropositive steers. After day 13, sensitivity of the cELISA and CF test was 100% and 20%, respectively. During peak parasitemia (day 20), sensitivity of the cELISA and CF test was 100%. Thereafter, sensitivity of the CF test fluctuated between 7.5% and 37.5%, whereas sensitivity of the cELISA remained at 100%. Overall sensitivity of the cELISA and CF test was 94.8% and 26.5%, respectively (κ statistic, 0.039).
Conclusions and Clinical Relevance—The cELISA had superior sensitivity for serologic detection of A marginale.The CF test and cELISA each had a high percentage of false-negative results during the prepatent period. These findings are relevant for export certification and anaplasmosis prevention or eradication programs.
Objective—To examine effects of danofloxacin and
tilmicosin on continuously recorded body temperature
in beef calves with pneumonia experimentally
induced by inoculation of Mannheimia haemolytica.
Animals—41 Angus-cross heifers (body weight, 160 to
220 kg) without a recent history of respiratory tract disease
or antimicrobial treatment, all from a single ranch.
Procedure—Radiotransmitters were implanted intravaginally
in each calf. Pneumonia was induced intrabronchially
by use of logarithmic-phase cultures of
M haemolytica. At 21 hours after inoculation, calves
were treated with saline (0.9% NaCl) solution,
danofloxacin, or tilmicosin. Body temperature was
monitored from 66 hours before inoculation until 72
hours after treatment. Area under the curve (AUC) of
the temperature-time plot and mean temperature
were calculated for 3-hour intervals and compared
among treatment groups.
Results—The AUCs for 3-hour intervals did not differ
significantly among treatment groups for any of the
time periods. Analysis of the mean temperature for
3-hour intervals revealed significantly higher temperatures
at most time periods for saline-treated calves,
compared with temperatures for antimicrobial-treated
calves; however, we did not detect significant differences
between the danofloxacin- and tilmicosin-treated
calves. The circadian rhythm of temperatures
before exposure was detected again approximately
48 hours after bacterial inoculation.
Conclusions and Clinical Relevance—Danofloxacin
and tilmicosin did not differ in their effect on mean
body temperature for 3-hour intervals but significantly
decreased body temperature, compared with body
temperature in saline-treated calves. Normal daily
variation in body temperature must be considered in
the face of respiratory tract disease during clinical
evaluation of feedlot cattle. ( Am J Vet Res 2004;65:
OBJECTIVE To determine whether animal-to-animal and community contact patterns were correlated with and predictive for bovine respiratory disease (BRD) in beef steers during the first 28 days after feedlot entry.
PROCEDURES Calves were instrumented with a real-time location system transmitter tag and commingled in a single pen. The location of each calf was continuously monitored. Contact between calves was defined as ≤ 0.5 m between pen coordinates, and the duration that 2 calves were within 0.5 m of each other was calculated daily. Bovine respiratory disease was defined as respiratory tract signs and a rectal temperature > 40°C. Locational data were input into a community detection program to determine daily calf contact and community profiles. The number of BRD cases within each community was determined. A random forest algorithm was then applied to the data to determine whether contact measures were predictive of BRD.
RESULTS Probability of BRD was positively correlated with the number of seconds a calf spent in contact with calves presumably shedding BRD pathogens and number of calves with BRD within the community on the day being evaluated and the previous 2 days. Diagnostic performance of the random forest algorithm varied, with the positive and negative predictive values generally < 10% and > 90%, respectively.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that direct transmission of BRD pathogens likely occurs among feedlot cattle. The relative contribution of animal-to-animal contact to BRD risk remains unknown and warrants further investigation.
Analytical precision and accuracy in residue chemistry are constantly improving toward the goal of a safe food supply. On July 6, 2012, the USDA FSIS announced a restructuring of the US NRP with respect to sampling of compounds in meat, poultry, and egg products and the scheduling of animal production classes.1 The FSIS has also implemented several new MRMs for analyzing tissue samples from harvested animals for violative residues. These MRMs allow for several compounds to be tested simultaneously. As a result, compounds that have not been previously tested in certain animal production classes are now included in
Objective—To optimize methods for the use of computed tomography (CT) to assess pathologic changes in the lungs of calves and to determine the effect of treatment on lung consolidation.
Animals—10 male Holstein calves.
Procedures—Calves were anesthetized to facilitate CT imaging of the thorax. After initial images were obtained, pneumonia was induced in the calves by inoculation through a bronchoscope. Two calves were used in a preliminary study to refine the inoculation dose and optimize CT images. Four calves were administered florfenicol and 4 calves were untreated control animals. Serial images were obtained 24, 48, and 72 hours after inoculation. After final images were obtained, calves were euthanized, and lung consolidation was estimated by use of lung surface area scoring and water displacement. These estimates were compared with estimated lung consolidation obtained by use of CT.
Results—Calves had rapid disease progression. Percentage of lung consolidation was not significantly different between treatment groups for any of the estimation methods. Results of an ANOVA of the 3 assessment methods indicated significant differences among methods. Estimates of the percentage of lung consolidation obtained by use of surface area scoring and CT correlated well, whereas water displacement estimates correlated poorly with other methods of consolidation estimation.
Conclusions and Clinical Relevance—Because of the correlation with other methods for estimation of lung consolidation, CT has the potential to be used to monitor disease progression in calves with experimentally induced respiratory tract disease.