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- Author or Editor: Michael D. Apley x
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Abstract
Objective—To determine the effects of 2 anti-inflammatory drugs in lactating Holstein cows with endotoxin- induced mastitis.
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)
Summary
Plasma and lung tissue pharmacokinetics of danofloxacin in calves with naturally induced acute pneumonia were determined in 2 separate studies. A maximal pneumonic tissue concentration of 1.17 μg/ g was achieved 1.8 hours after im injection of 1.25 mg of danofloxacin/kg of body weight. Pneumonic tissue danofloxacin concentrations were 5.5 times greater than those in plasma at 1 and 2 hours after injection. Cranioventral pneumonic tissue had significantly decreased danofloxacin concentration, compared with that of grossly normal tissue from the caudodorsal part of the lungs at 2 of 6 sample times.
After iv injection, the apparent steady-state volume of distribution was 3.44 ± 1.13 L/kg, and the elimination half-life was 6.26 ± 2.27 hours. Maximal plasma danofloxacin concentration of 0.25 μg/ml was detected 0.80 hour after im injection. Bioavailability was 91%.
Our findings indicated that a large percentage of danofloxacin is rapidly absorbed after im administration to calves with acute pneumonia. Extensive tissue penetration was suggested by a high steady-state volume of distribution and was indicated by high concentrations in pneumonic tissue.
Summary
Six calves with areas of pulmonary consolidation attributable to bronchopneumonia, and 6 calves with no areas of consolidation were given iv injections of danofloxacin. This injection was followed approximately 55 minutes later by injection of 15-μm radiolabeled microspheres to measure regional pulmonary blood flow.
Calves were euthanatized exactly 1 hour after the danofloxacin injection. Six samples for determination of danofloxacin concentration, each surrounded by 4 samples for determination of gamma emission counts, were taken from each lung. Additional samples focusing on the line of demarcation between consolidated and nonconsolidated tissue were taken from calves with pulmonary consolidation.
Data from calves with no areas of pulmonary consolidation indicated that blood flow was significantly reduced in the caudodorsal position of the left lung and the caudodorsal and cranioventral positions of the right lung, compared with that in other positions within the lungs. Danofloxacin concentrations in the cranioventral positions of the right and left lungs were significantly lower than those in the middle-dorsal positions.
Differences in danofloxacin concentrations and blood flow were analyzed in consolidated and nonconsolidated cranioventral and middle-ventral positions of the lungs from calves with pulmonary consolidation. Decreases in blood flow in consolidated lung tissue ranged from 83.3 to 91.7%. Danofloxacin concentrations in consolidated lung tissue were significantly reduced by 41% in the middle ventral position of the left lung.
The line of demarcation step study revealed a significant reduction of blood flow at 2 and 4 cm into consolidated lung tissue, with reductions of 84 and 88%, respectively. Danofloxacin concentration did not significantly decrease in consolidated tissue.
Abstract
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 Iowa.
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)
Abstract
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.
Abstract
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.
Abstract
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.
ANIMALS 70 weaned beef steers (mean weight, 248.9 kg).
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.
Abstract
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.
Abstract
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 × 109 A 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.
