Search Results

Abstract

Objective—To evaluate the association between fecal excretion of Mycobacterium avium subsp paratuberculosis (MAP) by dairy cows in the periparturient period and detection of MAP DNA in colostrum specimens and on teat skin surfaces.

Design—Cross-sectional study.

Animals—112 Holstein cows.

Procedures—Fecal specimens were collected within 48 to 72 hours prior to parturition, and colostrum and teat swab specimens were collected immediately after parturition. Detection of MAP in fecal specimens was performed via microbial culture, and detection of MAP DNA in colostrum and teat swab specimens was achieved via a PCR assay targeting the genetic element ISMAP02. Logistic regression was used to model the relationship between MAP fecal shedding status and detection of MAP DNA in colostrum or teat swab specimens. Population attributable fractions for the proportion of colostrum and teat swab specimens containing MAP DNA were also calculated.

Results—The odds of detecting MAP DNA in colostrum or teat swab specimens in cows with MAP-positive (vs negative) fecal specimens were 2.02 and 1.87 respectively. Population attributable fractions estimates suggested that withholding colostrum from MAP-positive cows could reduce the odds of exposing calves to MAP in colostrum by 18.2%. Not permitting natural suckling by calves could reduce the odds of exposing calves to MAP on the teat surfaces of MAP-positive cows by 19.5%.

Conclusions and Clinical Relevance—Results underscored the need for strict adherence to practices that limit contact of calves with adult cows from the time of birth and promote hygienic colostrum handling to avoid possible contamination with MAP during colostrum harvest, storage, or feeding.

Abstract

Objective—To estimate the risk of subclinical Mycobacterium avium subsp paratuberculosis (MAP) infection in cows that ingested MAP DNA–positive raw colostrum as calves, compared with risk in cows that ingested MAP DNA–negative raw colostrum as calves.

Animals—205 calves born in 12 commercial dairy herds.

Procedures—Each calf was separated from its dam within 30 to 60 minutes after birth and fed raw colostrum. For each calf, samples of the colostrum fed were collected and tested for the presence of MAP DNA by use of a nested PCR assay for the target gene ISMAP02. Calves fed colostrum positive or negative for MAP DNA were classified into exposed (n = 69) and unexposed (136) groups, respectively. Each calf was tested for MAP infection at 30, 42, and 54 months of age by use of a serum ELISA and bacterial culture of feces. Weibull hazard regression models were used to evaluate the association between exposure to MAP DNA–positive colostrum and time to testing positive for MAP infection.

Results—Hazard of MAP infection was not different between groups (exposed vs unexposed) when serum ELISA, bacterial culture of feces, or both diagnostic tests (parallel interpretation) were positive.

Conclusions and Clinical Relevance—Heifer calves fed MAP DNA–positive colostrum were at no greater risk of MAP infection, compared with heifer calves fed MAP DNA–negative colostrum. This result contradicts findings from other studies and should be interpreted with caution.

Abstract

Objective—To evaluate the effect of delayed exposure of dairy cattle to Mycobacterium avium subsp paratuberculosis (MAP) on the incidence of those cows testing positive for MAP and developing clinical Johne's disease (CJD).

Animals—79 cows not exposed to MAP as calves (unexposed cohort) and 260 cows exposed to MAP as calves (exposed cohort).

Procedures—Cows in the unexposed cohort were born into 5 MAP-uninfected herds and introduced at various ages into 5 MAP-infected herds where the exposed cohort cows were born and raised. Beginning when each cow was 24 months old, fecal and serum samples were collected annually from 2003 through 2006. Feces were cultured for MAP, and an ELISA was used to analyze serum samples for antibodies against MAP. Date and reason for culling were obtained from herd records. Incidence of positive culture and ELISA results and CJD was compared between unexposed and exposed cohort cows with Cox regression.

Results—Compared with exposed cohort cows, the hazard ratios for unexposed cohort cows having positive culture results, having positive ELISA results, and developing CJD were 0.12, 0.03, and 0.001, respectively, and those ratios increased by 2%, 6%, and 17%, respectively, for each month spent in an MAP-infected herd.

Conclusions and Clinical Relevance—Delayed exposure of cows to MAP resulted in lower incidences of positive culture and ELISA results and CJD in those cows, compared with incidences of cows exposed to MAP since birth. The hazard of testing positive for MAP or developing CJD increased with time, regardless of cohort.

Abstract

Objectives—To determine the sensitivity of bacteriologic culture of pooled fecal samples in detecting Mycobacterium paratuberculosis, compared with bacteriologic culture of individual fecal samples in dairy cattle herds.

Study Design—Cross-sectional study.

Animals—24 dairy cattle herds.

Procedure—Individual and pooled fecal samples were submitted for bacteriologic culture, and results were compared between these groups.

Results—Ninety-four and 88% of pooled fecal samples that contained feces from at least 1 animal with high (mean, ≥ 50 colonies/tube) and moderate (mean, 10 to 49 colonies/tube) concentrations of M paratuberculosis, respectively, were identified by use of bacteriologic culture of pooled fecal samples. Prevalences of paratuberculosis determined by bacteriologic culture of pooled and individual fecal samples were highly correlated.

Conclusions and Clinical Relevance—Bacteriologic culture of pooled fecal samples provided a valid and cost-effective method for the detection of M paratuberculosis infection in dairy cattle herds and can be used to estimate prevalence of infection within a herd. (J Am Vet Med Assoc 2003;223:1022–1025)

Abstract

Objective—To determine factors associated with implementation and use of an on-farm system for bacteriologic culture of milk from cows with lowgrade mastitis, including information on how producers used the on-farm bacteriologic culture system to guide antimicrobial selection practices and the resulting impact on patterns of antimicrobial use.

Design—Retrospective cohort study.

Sample Population—Producers of 81 dairy farms.

Procedure—Farms that used an on-farm system for bacteriologic culture of milk from January 2001 to July 2003 were surveyed.

Results—Over half of those producers continuing to use the on-farm culture delayed antimicrobial treatment pending results of bacteriologic culture. Most other producers initiated empirical antimicrobial treatment while bacteriologic culture results were pending. Several barriers to the use of an on-farm system were identified. Significant reductions in rates of antimicrobial use were detected when comparing antimicrobial use rates before and during use of the on-farm system. Most producers chose to treat cows with mastitis caused by gram-positive pathogens with antimicrobials, whereas treatment choices for cows with mastitis caused by gram-negative bacteria and in cases in which no growth was detected varied.

Conclusions and Clinical Relevance—Readily available results permit antimicrobial selections to be made on the basis of the causative agent of mastitis. Adoption of an on-farm system for bacteriologic culture of milk may result in significant reductions in the percentage of cows treated with antimicrobials. Decreasing antimicrobial use may have several benefits including preventing unnecessary discarding of milk, decreasing the potential for drug residues in milk, and improving treatment outcomes as a result of targeted treatments.

Abstract

Objective—To evaluate longevity, milk production, and breeding performance in adult Holstein cows fed either a plasma-derived commercial colostrum replacer (CR) or raw bovine maternal colostrum (MC) at birth.

Design—Randomized controlled clinical trial.

Animals—497 heifer calves born in 12 commercial dairies located in Minnesota and Wisconsin.

Procedures—All calves were separated from their dams within 30 to 60 minutes after birth and systematically assigned to be fed either MC (control group [n = 261 calves]) or CR (treatment group [236]). Calves were observed from birth up to adulthood (approx 54 months old), during which time death and culling events plus milk yield and breeding performance data were collected. Time to death, time to culling, time to death or culling combined, time to first calving, and time to conception intervals were evaluated by use of proportional hazards survival analysis models. Number of times inseminated per conception and lifetime milk yield (up to 54 months old) were evaluated by use of general linear models.

Results—Cows fed CR as calves at the time of birth were no different than cows fed MC as calves with respect to overall risk of death, culling, or death or culling combined (from birth to 54 months of follow-up and from first calving to 54 months old); lifetime milk yield; and breeding performance.

Conclusions and Clinical Relevance—No difference was detected in overall risk of death or culling, milk production, or reproductive performance between cows fed CR and those fed MC as calves at birth.

Abstract

Objective—To estimate the relative risk of paratuberculosis (Johne's disease [JD]) in calves fed a plasma-derived colostrum-replacement (CR) product versus raw bovine maternal colostrum (MC).

Study Design—Randomized controlled clinical trial.

Animals—497 heifer calves born in 12 JD-endemic commercial Holstein dairy farms located in Minnesota and Wisconsin.

Procedures—Every calf was separated from its dam within 30 to 60 minutes after birth and systematically assigned to be fed raw bovine MC (control group, n = 261 calves) or CR (treatment group, 236 calves). The calves were monitored to adulthood and tested for Mycobacterium avium subsp paratuberculosis (MAP) infection by use of an ELISA to detect serum antibodies against MAP and bacterial culture for MAP in feces at approximately 30, 42, and 54 months of age. Weibull regression models were used to evaluate the effect of feeding CR (vs raw bovine MC) on the risk of developing JD infection.

Results—Calves fed CR at birth were less likely (hazard ratio = 0.559) to become infected with MAP (as determined by use of an ELISA, bacterial culture, or both diagnostic tests), compared with the likelihood for calves fed MC at birth.

Conclusions and Clinical Relevance—This study revealed that feeding CR reduced the risk of developing MAP infection in Holstein calves born in JD-endemic herds, which implied that feeding raw bovine MC may be a source of MAP for calves. Plasma colostrum-replacement products may be an effective management tool for use in dairy herds attempting to reduce the prevalence of JD.

Abstract

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.

Abstract

Objective—To determine growth, morbidity, and mortality rates in dairy calves fed pasteurized nonsaleable milk versus commercial milk replacer and compare economics of feeding pasteurized nonsaleable milk versus commercial milk replacer in dairy calves.

Design—Clinical trial.

Animals—438 dairy calves.

Procedure—Calves were assigned at 1 to 2 days of age to be fed pasteurized nonsaleable milk or a commercial milk replacer until weaned. Body weight was measured at the time of study enrollment and at the time of weaning, and any medical treatments administered and deaths that occurred prior to weaning were recorded. A partial budget model was developed to examine the economics of feeding pasteurized nonsaleable milk versus commercial milk replacer.

Results—Calves fed conventional milk replacer had significantly lower rates of gain (–0.12 kg/d [–0.26 lb/d]), lower weaning weights (–5.6 kg [–12.3 lb]), higher risk for treatment during the summer and winter months (odds ratio [OR], 3.99), and higher risk of death during the winter months (OR, 29.81) than did calves fed pasteurized nonsaleable milk. The estimated savings of feeding pasteurized nonsaleable milk, compared with milk replacer, was $0.69/calf per day. The estimated number of calves needed to economically justify the nonsaleable milk pasteurization system was 23 calves/d.

Conclusions and Clinical Relevance—Results suggest that dairy calves fed pasteurized nonsaleable milk have a higher growth rate and lower morbidity and mortality rates than do calves fed conventional milk replacer. Feeding pasteurized nonsaleable milk could be an economically viable strategy for dairy calf producers. (J Am Vet Med Assoc 2005;226:1547–1554)

Abstract

Objective—To determine the effect of oral administration of dantrolene sodium on serum creatine kinase (CK) activity after exercise in horses with recurrent exertional rhabdomyolysis (RER).

Animals—2 healthy horses and 5 Thoroughbreds with RER.

Procedure—3 horses received 2 doses of dantrolene (4, 6, or 8 mg/kg, PO, with and without withdrawal of food) 2 days apart; 90 minutes after dosing, plasma dantrolene concentration was measured spectrofluorometrically. On the basis of these results, 5 Thoroughbreds with RER from which food was withheld received dantrolene (4 mg/kg) or an inert treatment (water [20 mL]) orally 90 minutes before treadmill exercise (30 minutes, 5 d/wk) during two 3-week periods. Serum CK activity was determined 4 hours after exercise. Plasma dantrolene concentration was measured before and 90 minutes after dosing on the first and last days of dantrolene treatment and before dosing on the first day of the inert treatment period.

Results—90 minutes after dosing, mean ± SEM plasma dantrolene concentration was 0.62 ± 0.13 and 0 µg/mL in the dantrolene and inert treatment groups, respectively. Serum CK activity was lower in dantrolene- treated horses (264 ± 13 U/L), compared with activity in water-treated horses (1,088 ± 264 U/L). Two horses displayed marked muscle stiffness on the inert treatment.

Conclusions and Clinical Relevance—In 5 horses with RER from which food had been withheld, 4 mg of dantrolene/kg administered orally provided measurable, though variable, plasma concentrations and significantly decreased serum CK activity after exercise in 4 of those horses. ( Am J Vet Res 2004; 65:74–79)