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- Author or Editor: Ken E. Leslie x
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Objective—To determine whether half-udder intramammary infusion of cloxacillin results in transfer of cloxacillin from treated to untreated mammary gland quarters within nonlactating cows, and, if so, at what concentrations, and to determine whether selection of ipsilateral versus diagonal-contralateral quarters for treatment affects cloxacillin transfer among quarters.
Animals—20 Holstein-Friesian cows from a dairy herd.
Procedures—A within-cow half-udder comparison trial was used in which 2 of 4 mammary gland quarters (ipsilaterally or diagonally) received an intramammary infusion of cloxacillin on day 1 of the nonlactating period. Three days later, milk samples were taken from all untreated quarters and high-pressure liquid chromatography was used to detect and quantify milk cloxacillin concentrations.
Results—Cloxacillin was detected in 25% of all untreated mammary gland quarters. Mean cloxacillin concentration in untreated quarters was below minimum inhibitory concentrations for targeted mastitis pathogens. No significant difference in cloxacillin concentrations was found in the ipsilateral or diagonal treatment groups.
Conclusions and Clinical Relevance—Within-cow half-udder comparison trials are valid for antimicrobial trials in nonlactating cows, although transfer of antimicrobials does occur in trace concentrations. Ipsilateral or diagonal-contralateral treatment designs perform similarly. This type of design is economical for researchers, although care must be taken to account for within-cow clustering of mammary gland quarter data.
OBJECTIVE To investigate the association of bovine respiratory disease (BRD) or vaccination with serologic response in calves.
ANIMALS 94 Holstein calves.
PROCEDURES To assess the association between BRD and antibody titers, 38 calves < 3 months old that were treated for BRD were matched with 38 untreated calves. To investigate the effect of vaccination on antibody titers, 24 calves were randomly assigned to be vaccinated against bovine respiratory syncytial virus (BRSV), bovine viral diarrhea virus types 1 and 2, bovine herpesvirus type 1 (BHV1), and parainfluenza virus type 3 at 2 weeks of age (n = 6), 5 weeks of age (6), and both 2 and 5 weeks of age (6) or were assigned to be unvaccinated controls (6). Blood samples were obtained at I, 2, 5, and 12 weeks for determination of serum neutralization antibody titers against the vaccine viruses, bovine coronavirus, and Mannheimia haemolytica. Antibody rates of decay were calculated.
RESULTS Calves with initial antibody titers against BRSV < 1:64 that were treated for BRD had a slower rate of anti-BRSV antibody decay than did similar calves that were not treated for BRD. Calves with high initial antibody titers against BRSV and BHV1 had lower odds of BRD than did calves with low initial antibody titers against those 2 pathogens. Vaccination at 2 or 5 weeks of age had no effect on the rate of antibody decay.
CONCLUSIONS AND CLINICAL RELEVANCE Clinical BRD and the serologic response of dairy calves were associated with initial antibody titers against BRSV and BHV1. Serologic or clinical responses to viral exposure may differ in calves with low passive immunity.
Objective—To identify serum biochemical and hematologic variables, as measured in the week before parturition, that predict postpartum retention of the placenta (RP) in dairy cows.
Design—Retrospective cohort study.
Animals—1,038 cows in 20 commercial dairy herds.
Procedures—Serum concentrations of fatty acids (FAs), β-hydroxybutyrate, cholesterol, glucose, urea, and calcium and blood leukocyte, neutrophil, lymphocyte, monocyte, and eosinophil counts were determined. These variables were evaluated for an association with development of RP by use of a multivariate logistic regression model. Parity, season of par-turition, existence of twins or dystocia, body condition score, and vitamin E treatment were included in the model as covariates.
Results—High serum concentrations of cholesterol and FAs were associated with an increased odds of RP. There was a 5% relative increase in the odds of RP for each 0.1 mmol/L increase in cholesterol or FAs concentration in the week before parturition. Season of parturition and twinning were also identified as risk factors.
Conclusions and Clinical Relevance—These associations indicated that prepartum energy metabolism contributes to the development of RP. Serum concentrations of cholesterol and FAs may be useful to identify cows with a metabolic abnormality or energy imbalance that might predispose them to RP and should be interpreted in conjunction with clinical risk factors such as twinning, dystocia, or parturient paresis.
Objective—To determine whether results obtained for milk and serum samples with ELISAs intended for diagnosis of paratuberculosis in dairy cows were comparable to results obtained by means of mycobacterial culture of fecal samples.
Animals—689 lactating dairy cows in 9 Ontario herds.
Procedure—Milk, serum, and fecal samples were obtained from all cows. Fecal samples were submitted for mycobacterial culture. Serum samples were tested with a commercially available ELISA for antibodies against Mycobacterium paratuberculosis, and preserved milk samples were tested with an indirect ELISA for antibodies against M paratuberculosis.
Results—Results were positive for 130 of the 689 (18.9%) serum samples, 77 of the 689 (11.1%) milk samples, and 72 of the 689 (10.4%) fecal samples. The level of agreement between results for milk and serum samples was only moderate. Proportions of positive results for serum and fecal samples were significantly different, but proportions of positive results for milk and fecal samples were not significantly different. In addition, results for milk samples had a higher level of agreement with results of mycobacterial culture than did results for serum samples.
Conclusions and Clinical Relevance—Results suggest that the indirect ELISA used on milk samples may be a convenient method of detecting paratuberculosis in dairy herds. (J Am Vet Med Assoc 2005; 226:424–428)
Objective—To determine the effect of paratuberculosis on culling, milk production, and milk quality in infected dairy herds.
Animals—689 lactating dairy cows in 9 herds.
Procedure—Milk, blood, and fecal samples were obtained from all cows. Fecal samples were evaluated via mycobacterial culture. Serum samples were tested with a commercially available ELISA for antibodies against Mycobacterium avium subsp paratuberculosis, and preserved milk samples were tested with an ELISA for antibodies against M paratuberculosis. Mixed effect and proportional hazards models were used to determine the effect of paratuberculosis on 305-day milk, fat, and protein production; somatic cell count linear score; and the risk of culling.
Results—Cows with positive results of bacteriologic culture of feces and milk ELISA produced less milk, fat, and protein, compared with herdmates with negative results. No difference in 305-day milk or fat production was detected in cows with positive results of serum ELISA, compared with seronegative cows. The 3 survival analyses revealed that cows with positive results of each test were at higher risk of being culled than cows with negative results. Paratuberculosis status, as determined by use of all 3 diagnostic tests, was not associated with milk somatic cell count linear score.
Conclusions and Clinical Relevance—Results suggest that for the 9 herds in this study, paratuberculosis significantly decreased milk production and cow longevity. (J Am Vet Med Assoc 2005;227:1302–1308)
Objective—To determine whether insertion of an internal teat sealer (ITS) at the end of lactation would prevent development of new intramammary infections (IMIs) during the nonlactating period.
Design—Controlled clinical trial.
Animals—939 Holstein-Friesian dairy cows from 16 herds.
Procedures—Results of bacteriologic culture of milk samples collected 14 days prior to the end of lactation were used to assign cows to groups (group 1 = negative results for all quarters; group 2 = positive results for ≥ 1 quarter). Quarters of cows in group 1 were treated with an ITS or a single intramammary dose of cloxacillin; quarters of cows in group 2 were treated with cloxacillin in conjunction with an ITS or with cloxacillin alone. Milk samples were collected at the end of lactation and within 8 days after calving.
Results—Regardless of whether the outcome of interest was new IMIs caused by any pathogens, major pathogens, environmental pathogens, or streptococci other than Streptococcus agalactiae, quarters in group 2 treated with both cloxacillin and an ITS were less likely to develop a new IMI than were quarters treated with cloxacillin alone. For cows in group 1, no significant difference in risk of new IMIs was found between treatments.
Conclusions and Clinical Relevance—Results suggest that for dairy cattle with an IMI late in the lactation period, intramammary administration of cloxacillin at the end of lactation followed by insertion of an ITS enhanced protection against development of new IMIs, compared with use of cloxacillin alone.
Objective—To determine whether Neospora caninum serostatus was associated with milk production among Holstein cattle in Ontario.
Design—Case-control study and cross-sectional observational study.
Animals—3,702 Holstein cows in 83 herds (casecontrol study) and 3,162 Holstein cows in 57 herds.
Procedure—Herds in the case-control study were grouped on the basis of N caninum abortion status. Herds in the observational study were considered representative of Ontario dairy herds. The N caninum serostatus of individual cows was determined with a kinetic ELISA. Milk production was modeled to compare seropositive with seronegative animals while controlling for parity, days since parturition, and herd clustering.
Results—In the case-control study, 305-day milk production of seropositive cows was significantly less than milk production of seronegative cows in herds with abortions attributable to N caninum infection and in herds with abortions attributable to pathogens other than N caninum, but not in herds without abortion problems. In the observational study, 305-day milk production for seropositive cows was not significantly different from milk production of seronegative cows.
Conclusions and Clinical Relevance—Results suggest that the association between N caninum serostatus and milk production in Ontario Holstein dairy cattle may depend on abortion status of the herd. In herds with abortion problems, regardless of cause, N caninum-seropositive cattle produced less milk, whereas in herds without abortion problems, N caninum-seropositive cattle produced the same amount of milk as seronegative cattle. (J Am Vet Med Assoc 2002;221:1160–1164)