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in Journal of the American Veterinary Medical Association

Objective

To determine the prevalence of Mycoplasma spp in herds that were members of a milk cooperative.

Design

Epidemiologic study.

Sample Population

267 dairy herds that were members of a milk cooperative.

Procedure

Bulk-tank milk samples were collected monthly during a 6-year period from all dairies in the cooperative. Samples were submitted to the cooperative's laboratory for bacterial culture for Mycoplasma spp, using direct plating. Milk samples positive for Mycoplasma organisms were speciated.

Results

Prevalence of positive samples varied from 1.8 to 5.8% for all species of Mycoplasma and from 1.2 to 3.1% for Mycoplasma spp known to be mastitis pathogens. One mycoplasmal species was isolated initially on 99 of 198 (50.0%) dairies, but 68 of 198 (34.3%) dairies had 2 species isolated. Mycoplasma bovis, M californicum, and M bovigenitalium were consistently isolated, but M bovis (243/499; 48.6%) was the most commonly isolated species. Acholeplasma laidlawii was more prevalent in 1989 and 1995 than other years. Mycoplasma bovigenitalium and M californicum had a seasonal distribution. Less than 50 colonies per plate were isolated for most (317/500; 63.4%) bulk-tank samples. Of the milk samples with > 100 colonies/plate, Mycoplasma bovis was isolated most frequently (73/243; 30.0%).

Clinical Implications

Distribution of Mycoplasma spp varied by year, number of colonies isolated per sample, season, and herd. Therefore, it may be necessary to routinely sample bulk-tank milk, and all isolates should be speciated. Culture results from milk cooperatives should be used with other monitoring information to determine the Mycoplasma status of herds. (J Am Vet Med Assoc 1997;211:1036–1038)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the prevalence of Salmonella spp in wild birds commonly found on California dairies.

Design—Prospective study.

Animals—7 selected species of birds were captured on 9 dairies in Kings and Tulare counties, California.

Procedure—Birds were captured (using traps and nets) and euthanatized, and the entire gastrointestinal tract was removed. Contents of the gastrointestinal tract were subjected to culture for Salmonella spp.

Results—892 birds were captured, and Salmonella spp were isolated from 22 birds. The prevalence by dairy ranged from 0.7 to 16.7%, whereas the prevalence by bird species ranged from 1.2 to 3.2%. Cowbirds and English sparrows had the highest prevalence of Salmonella organisms. Five serotypes of Salmonella organisms were isolated, including Meleagridis, Montevideo, Muenster, Typhimurium, and an untyped serotype.

Conclusions and Clinical Relevance—On the basis of our findings, birds that commonly inhabit California dairies harbor Salmonella organisms. However, because of the low prevalence of Salmonella organisms in birds and the Salmonella serotypes isolated, birds are not important reservoirs of Salmonella organisms on California dairies. (J Am Vet Med Assoc 2002;220:359–362)

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in Journal of the American Veterinary Medical Association

Objective

To determine whether treatment with a commercially available nonspecific immunomodulating biologic product would alter the clinical course of disease in neonatal calves.

Design

Systematically randomized, controlled cohort study.

Animals

200 Holstein bull calves 1 to 5 days old.

Procedure

Assessments were performed that included evaluation of fecal consistency, attitude, appetite, and hydration status. Calves with abnormal results were enrolled in the study. Calves were systematically assigned to control or treatment groups (100 calves/group). Calves in the treatment group were given a single IV injection of the biologic product at the time of enrollment, whereas control calves were not given the product. Calves were assessed daily for 5 days to evaluate fecal consistency, attitude, appetite, hydration status, and rectal temperature. Assessments were made without knowledge of group assignment.

Results

Treatment with the immunomodulating product was not associated with a decrease in the number of calves that had moderate or severe departures from clinically normal conditions for attitude, appetite, or hydration on days 1 though 5, compared with control calves. Fecal consistency scores were significantly greater for treated calves on days 1 (P = 0.03) and 5 (P = 0.02), compared with scores for control calves.

Clinical Implications

Administration of the nonspecific immunomodulating biologic product did not significantly affect outcome of clinical disease for calves in the treated group, compared with calves in the control group. On the basis of results of this study, we cannot recommend use of the nonspecific immunomodulating biologic product for the treatment of undifferentiated diarrheal disease in neonatal calves. (J Am Vet Med Assoc 1998;213:1308-1311)

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in Journal of the American Veterinary Medical Association

Objective—

To determine whether treating cows with antimicrobials at the end of lactation would lower the incidence of clinical mastitis, improve milk production, and decrease somatic cell count (SCC) in the subsequent lactation.

Design—

Randomized blind field trial.

Animals—

233 Holstein cows from a single herd. All cows were in lactation 2 or greater.

Procedure—

Cows were randomly assigned to treatment groups. Treated cows were given procaine penicillin G and novobiocin by intramammary infusion. Control cows were not treated. Farm personnel recorded cases of clinical mastitis. Milk yield and SCC were recorded during the subsequent lactation.

Results—

Treatment did not significantly reduce the incidence of clinical mastitis when data for all cows were grouped or when data were stratified by lactation groups (lactation 2 vs lactation ≥ 3) or by last SCC (≤ 500,000 cells/ml vs > 500,000 cells/ml). Somatic cell counts (first, mean of first 5, maximum of first 5) for treated and control cows were similar, and proportions of treated and control cows with SCC > 500,000 cells/ml at least once were not significantly different. Treated cows produced 179 kg (394 lb) more milk during the first 17 weeks of lactation than did control cows.

Clinical Implications—

Treating cows with antimicrobials at the end of lactation increased 17-week milk production during the subsequent lactation and, at current milk prices, was financially preferable to not treating them. (J Am Vet Med Assoc 1997;211:207–211)

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in Journal of the American Veterinary Medical Association

Objective

Validate, by sensitivity and specificity analyses, use of somatic cell count (SCC) to predict bacteriologically positive subclinical mastitis in a California dairy herd with low SCC.

Design

Study of monthly dairy herd improvement SCC obtained from the immediate preceding lactation and individual cow composite milk sample microbiologic isolates collected at calving.

Animals

515 California dairy cows with SCC and culture data.

Procedure

Somatic cell count sensitivity and specificity analyses with combinations of SCC parameter and at various thresholds were done, using the bacterial isolates as the standard.

Results

Combination of SCC threshold and SCC parameters could not be developed that had sufficient sensitivity and specificity to be a useful predictor of cows that would calve with subclinical mastitis.

Clinical Implication

Under the conditions at this particular dairy, SCC could not be used as a basis of prediction of cows that would calve with bacteriologically positive subclinical mastitis or require selective nonlactating-cow antibiotic treatment. (J Am Vet Med Assoc 1996;208:1054–1057)

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in Journal of the American Veterinary Medical Association

SUMMARY

Selenium concentration was measured in paired maternal blood samples and fetal liver specimens collected at a San Joaquin County, Calif, slaughterhouse (beef = 19, dairy = 54) and from bovine aborted fetuses submitted to the California Veterinary Diagnostic Laboratory System (CVDLS; beef = 20, dairy = 20). Of the slaughterhouse samples and specimens, dairy maternal blood selenium concentration was significantly (P < 0.001) higher (mean ± sd; 0.22 ± 0.056 µg/ml) than that for beef breeds (0.137 ± 0.082 µg/ml). The CVDLS mean maternal blood selenium concentration for the dairy-breed samples (0.192 ± 0.028 µg/ml) was similar to that for the slaughterhouse dairy-breed samples, but was greater than that for the slaughterhouse beef-breed samples. Slaughterhouse mean fetal liver selenium content also was higher (P < 0.001) for the dairy breeds (0.777 ± 0.408 µg/g), compared with the beef breeds (0.443 ± 0.038 µg/g). Mean fetal liver selenium content for slaughterhouse specimens was higher (P < 0.002) than that for the CVDLS specimens (beef, 0.244 ± 0.149 µg/g; dairy, 0.390 ± 0.165 µg/g). At the CVDLS, dairy fetal liver content was greater (P < 0.001) than that for beef breeds. Mean ratio of fetal liver selenium content to maternal blood selenium concentration was 3.53 ± 1.89 for dairy breeds at the slaughterhouse (liver-to-blood correlation [r] = 0.38), and was 2.11 ± 1.00 for dairy breeds at the CVDLS (r = 0.31) and 3.43 ± 1.50 for beef breeds (r = 0.58). Both slaughterhouse breed ratios were significantly (P < 0.002) greater than the CVDLS dairy-breed ratio. On the basis of these results, breed and source location should be taken into account when interpreting selenium values. Fetal liver selenium content should only be used as a screening test and combined with whole blood selenium concentration from clinically normal herdmates to evaluate herd selenium status.

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in American Journal of Veterinary Research

Summary

Milk production was monitored in 16 cows for 6 milkings after intramammary infusion of 1 mg of endotoxin in a single forequarter. The cows were randomly assigned to 1 of 2 treatment groups; 8 cows were treated with isotonic saline solution and 8 cows were treated with hypertonic saline solution. Saline solutions were administered IV (5 ml/kg of body weight) 4 hours after infusion of endotoxin. Mean cumulative change in milk yield and interval change in milk yield were greater in cows treated with isotonic saline solution than in cows treated with hypertonic saline solution. Significant differences between treatment groups were not detected.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the effect of daily oral administration of decoquinate to neonatal calves experimentally challenged with various numbers of Cryptosporidium parvumo ocysts.

Design—Clinical trial.

Animals—75 calves.

Procedure—Calves were purchased from a commercial dairy during a 5-week period. Calves were housed in individual hutches and fed milk replacer with or without decoquinate (2 mg/kg [0.9 mg/lb per day]). Calves were randomly assigned to treatment and 1 of 5 challenge groups (0, 50, 100, 1000, or 10,000 C parvum oocysts in 60 mL of saline [0.9% NaCl] solution administered PO on the day after arrival). Calves were maintained in the study for as long as 28 days. Calves were clinically assessed for diarrhea and dehydration. Fecal samples were submitted for oocyst enumeration 3 times each week.

Results—Treatment did not affect number of days to first watery feces (diarrhea), number of days to first oocyst shedding, or duration of diarrhea or oocyst shedding. Duration of oocyst shedding was significantly associated with challenge dose of oocysts administered to calves and number of days to first oocyst shedding. Duration of diarrhea and number of days to first oocyst shedding were significantly associated with week of arrival and number of days to first watery diarrhea.

Conclusions and Clinical Relevance—Daily treatment with decoquinate at the dosage used in this study did not affect oocyst shedding or clinical signs associated with cryptosporidiosis. However, there was an indication that if the number of oocysts calves received could be reduced, then the duration of oocyst shedding and, hence, environmental loading of C parvum oocysts could be reduced. (J Am Vet Med Assoc 2003;223:839–845)

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in Journal of the American Veterinary Medical Association