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- Author or Editor: Todd F. Duffield x
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Objective—To evaluate the use of a handheld device for measurement of β-hydroxybutyrate (BHBA) concentration to identify prepartum dairy cattle at risk of developing hyperketonemia during the first week after parturition.
Animals—210 prepartum dairy cows from 6 herds.
Procedures—A blood sample was collected from each cow 3 to 9 days before its expected calving date. β-Hydroxybutyrate concentration was immediately measured with a handheld device. Serum was harvested from the remaining sample and submitted to a laboratory for measurement of BHBA and nonesterified fatty acid (NEFA) concentrations. β-Hydroxybutyrate concentration determined with the handheld device was compared with that determined by laboratory methods. The association between prepartum BHBA concentration and the development of hyperketonemia (BHBA concentration, ≥ 1.2 mmol/L) during the first week after parturition was determined. The agreement between prepartum BHBA and NEFA concentrations for identification of cows at risk of developing postpartum hyperketonemia was evaluated.
Results—β-Hydroxybutyrate concentration determined by the handheld device was moderately correlated with that determined by laboratory methods. Cows with a prepartum BHBA concentration ≥ 0.6 mmol/L were 2.2 times as likely to develop hyperketonemia within 1 week after parturition as were cows with a prepartum BHBA concentration < 0.6 mmol/L. There was substantial agreement between prepartum BHBA and NEFA concentrations for identification of cows at risk of developing postpartum hyperketonemia.
Conclusions and Clinical Relevance—Results indicated the handheld device was a valid tool for measurement of BHBA concentration in prepartum dairy cattle, and measurement of prepartum BHBA concentration may be helpful for identifying cows at risk of developing postpartum hyperketonemia.
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 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 time until culling or risk of culling was associated with Neospora caninum serostatus among Holstein cattle in dairy herds in Ontario.
Design—Retrospective cohort study.
Animals—3,412 cows in 56 herds.
Procedure—Blood samples were collected, and serum was tested for antibodies against N caninum. Information on cows that were culled was collected during the 1- to 2-year period that producers were unaware of serostatus of individual cows in their herds.
Results—Herd prevalence of N caninum-seropositive cows ranged from 0 to 68.3% (median, 7.0%). During the time of the study, 184 of 359 (51.3%) N caninum-seropositive cows were culled, compared with 1,388 of 3,053 (45.5%) seronegative cows. Mean time from blood sample collection to culling for seronegative cows (289 days; 95% confidence interval, 280 to 299 days) was not significantly different from mean time for seropositive cows (296 days; 95% confidence interval, 269 to 323 days). Survival analysis indicated that N caninum serostatus was not associated with time to culling or risk of culling.
Conclusions and Clinical Relevance—Results suggest that N caninum serostatus of Holstein cows in Ontario was not significantly associated with either time to culling or risk of culling. Thus, N caninum serostatus alone should not be used to determine whether cows should be culled. (J Am Vet Med Assoc 2002;221:1165–1168)
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)