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  • Author or Editor: Pamela L. Ruegg x
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Abstract

Objective—To determine whether there was any association between results of in vitro antimicrobial susceptibility testing of pathogens isolated from cows with mild or moderate clinical mastitis and outcome of treatment.

Design—Observational study.

Animals—133 cows with mild or moderate mastitis in a single quarter.

Procedure—Cows were treated by means of intramammary infusion of pirlimycin (50 mg) in the affected quarter once daily for 2 days; additional intramammary treatments with the same product were administered if the milk continued to appear abnormal. Duration of treatment and days until clinical cure were recorded. Bacterial isolates were tested for antimicrobial susceptibility by means of a broth micro-dilution technique.

Results—Environmental streptococci, coliforms, and coagulase-negative Staphylococcus spp were the most commonly isolated pathogens. Duration of treatment and days until clinical cure were not significantly different for cows from which pathogens that were susceptible or resistant to pirlimycin were isolated. Bacteriologic cure rates 14 and 21 days after treatment were not significantly different for cows with mastitis caused by susceptible or resistant bacteria. Similar results were found when data only from cows with mastitis caused by gram-positive isolates were analyzed.

Conclusions and Clinical Relevance—In the present study, differences in clinical outcome for cows with mild or moderate mastitis that could be attributed to differences in results of in vitro susceptibility testing were not identified. The use of in vitro susceptibility testing to guide intramammary mastitis treatment cannot be recommended on the basis of results of this study. (J Am Vet Med Assoc 2005;227:1461–1468)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the association between results of in vitro antimicrobial susceptibility tests and outcomes in cows that received intramammary treatment with pirlimycin hydrochloride for subclinical mastitis associated with gram-positive pathogens.

Design—Case-control study.

Animals—132 dairy cows (178 mammary glands with subclinical mastitis caused by 194 pathogen isolates).

Procedures—Cows with positive results for a California mastitis test (CMT) were assigned to receive 50 mg of pirlimycin via intramammary administration into each CMT-positive mammary gland every 24 hours for 2 consecutive days or no treatment. Duplicate milk samples were collected before treatment and approximately 21 days later. Target pathogens included coagulase-negative Staphylococcus spp (n = 118 isolates), Streptococcus spp (28), Staphylococcus aureus (7), and other gram-positive cocci (30). Antimicrobial susceptibilities were determined via broth microdilution.

Results—Overall treatment success rate was 66% (128/194) for both groups. In vitro resistance to pirlimycin ranged from 0% (0/7 isolates of S aureus) to 50% (13/26 isolates of other gram-positive cocci). For the treated group, 62 of 94 (66%) target pathogens were classified as treatment successes and 32 (34%) were classified as failures. Similarly for the control group, 66 of 100 (66%) target pathogens were classified as treatment successes, whereas 34 (34%) were classified as failures.

Conclusions and Clinical Relevance—Many target pathogens from cows with subclinical mastitis were eliminated without treatment, and treatment with pirlimycin did not improve the treatment success rate. Results of in vitro antimicrobial susceptibility tests were not useful as predictors of treatment success following intramammary treatment with pirlimycin.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether antimicrobial resistance patterns of major mastitis pathogens isolated from milk samples from dairy cows have changed over time.

Design—Retrospective study.

Sample Population—8,905 bacterial isolates obtained from milk samples submitted to the Wisconsin Veterinary Diagnostic Laboratory between January 1994 and June 2001.

Procedure—Antimicrobial susceptibility was determined by means of the Kirby-Bauer disk diffusion method. Logistic regression was used to determine whether percentages of isolates resistant to various antimicrobials changed over time.

Results—For the gram-positive mastitis pathogens, percentages of isolates resistant to various β-lactam antimicrobials did not increase over the course of the study. Percentage of Staphylococcus aureus isolates resistant to penicillin decreased from 49 to 30%; percentage of Streptococcus isolates resistant to penicillin decreased from 6 to 1%. Percentage of isolates resistant to erythromycin increased for S aureus, Escherichia coli, Enterobacter spp, Enterococcus spp, and Pasteurella spp. Percentage of isolates resistant to lincomycin increased for S aureus and Staphylococcus spp. Percentage of coagulase-negative Staphylococcus isolates resistant to pirlimycin increased from 6 to 19%. For several pathogens, percentages of isolates resistant to sulfisoxazole and to trimethoprim-sulfamethoxazole decreased. No pathogens had a significant increase in the percentage of isolates resistant to novobiocin-penicillin.

Conclusions and Clinical Relevance—Results did not indicate a trend toward increased antimicrobial resistance among mastitis pathogens isolated from milk samples from dairy cows between 1994 and 2001. Reduced resistance to β-lactam antimicrobials was identified for several gram-positive mastitis pathogens. (J Am Vet Med Assoc 2003;222:1582–1589)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate enterotoxin production, enterotoxin gene distribution, and genetic diversity of Staphylococcus aureus in milk obtained from cows with subclinical mastitis.

Sample—Milk samples obtained from 350 cows (1,354 mammary glands) on 11 Wisconsin dairy farms.

Procedures—Of 252 S aureus isolates obtained from 146 cows, 83 isolates (from 66 cows with subclinical mastitis) were compared genotypically by use of pulsed-field gel electrophoresis and via PCR identification of toxic shock syndrome toxin 1 (TSST-1) and classical S aureus enterotoxin genes (sea, seb, sec, sed, and see).

Results—Among the 83 S aureus isolates, ≥ 1 enterotoxin genes were identified in 8 (9.6%). Enterotoxin gene distribution was as follows: TSST-1, 7 isolates (8.4%); sec, 5 isolates (6.0%); and sed, 2 isolates (2.4%). Enterotoxin genes sea, seb, and see were not identified. Twelve pulsotypes and 5 subtypes were identified among the 83 isolates; 5 of the 12 pulsotypes were represented by only 1 isolate. In cows of 1 herd, only a single S aureus pulsotype was detected; in cows on most other farms, a variety of pulsotypes were identified. One pulsotype was recovered from 4 farms (n = 23 cows) and another from 5 other farms (16). Isolates with an enterotoxin gene were represented by 6 pulsotypes.

Conclusions and Clinical RelevanceS aureus classical enterotoxins and TSST-1 were rarely recovered from milk samples obtained from cows with subclinical mastitis in Wisconsin. Diverse pulsotypes of S aureus were detected within and among farms, indicating that different strains of S aureus cause subclinical mastitis in dairy cows.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

The objective of this pilot study was to determine if an alternative dosing schedule of pegbovigrastim (PEG; Imrestor; Elanco Animal Health) affects mammary gland health, rear udder width, or milk production of healthy dairy cows.

ANIMALS

20 pregnant late-lactation Holstein cows in November 2019 through April 2020.

PROCEDURES

Cows were randomly assigned to receive subcutaneous injections with either 15 mg of PEG (PEG group; n = 10) or a sham injection with saline (0.9% NaCl) solution (control group; 10) administered 7 days before dry-off and at dry-off. Quarter milk samples were collected for bacterial culture and somatic cells before and after dry-off and after calving. Mammary gland width was assessed before and after dry-off. Daily milk yields were evaluated after calving.

RESULTS

The incidence of intramammary infection was 5 times greater for quarters of cows in the control group than for quarters of cows that received PEG. The effect of treatment on somatic cell count was not significant, but the effects of period and a treatment-by-period interaction were identified. Treatment did not significantly affect milk production in the subsequent lactation, but the effects of period and an interaction of treatment by period were identified. Rear udder width after dry-off was not significantly affected by treatment, but an effect of period was identified.

CLINICAL RELEVANCE

In this pilot study, cows treated with PEG using an alternative dosing schedule had reduced incidence of intramammary infection and an interaction of treatment by sampling period was observed for milk yield. These results suggest that further studies with larger numbers of cows are warranted.

Open access
in American Journal of Veterinary Research

Abstract

Objective—To compare the minimum inhibitory concentration (MIC) of cephapirin and ceftiofur with MICs of their active metabolites (desacetylcephapirin and desfuroylceftiofur) for selected mastitis pathogens.

Sample—488 mastitis pathogen isolates from clinically and subclinically affected cows in commercial dairy herds in Wisconsin.

Procedures—Agar dilution was used to determine MICs for Staphylococcus aureus (n = 98), coagulase-negative staphylococci (99), Streptococcus dysgalactiae (97), Streptococcus uberis (96), and Escherichia coli (98).

Results—All S aureus isolates were susceptible to cephapirin and ceftiofur. Most coagulase-negative staphylococci were susceptible to cephapirin and ceftiofur. For E coli, 50 (51.0%; cephapirin) and 93 (94.95%; ceftiofur) isolates were susceptible to the parent compounds, but 88 (89.8%) were not inhibited at the maximum concentration of desacetylcephapirin. All S dysgalactiae isolates were susceptible to ceftiofur and cephapirin, and consistent MICs were obtained for all compounds. Most S uberis isolates were susceptible to cephapirin and ceftiofur. Of 98 S aureus isolates classified as susceptible to ceftiofur, 42 (42.9%) and 51 (52%) were categorized as intermediate or resistant to desfuroylceftiofur, respectively. For 99 coagulase-negative staphylococci classified as susceptible to ceftiofur, 45 (45.5%) and 17 (17.2%) isolates were categorized as intermediate or resistant to desfuroylceftiofur, respectively. For all staphylococci and streptococci, 100% agreement in cross-classified susceptibility outcomes was detected between cephapirin and desacetylcephapirin. No E coli isolates were classified as susceptible to desacetylcephapirin.

Conclusions and Clinical Relevance—Differences in inhibition between parent compounds and their active metabolites may be responsible for some of the variation between clinical outcomes and results of in vitro susceptibility tests.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To identify management factors associated with veterinary usage by organic and conventional dairy farms.

Design—Prospective case-control study.

Sample—292 farms.

Procedures—Organic farms in New York, Oregon, and Wisconsin were matched to conventional farms on the basis of location and herd size. During a single herd visit, a questionnaire was administered, information about animal disease incidence and number of veterinarian visits in the preceding 60 days was collected, and forms to record similar information during the 60 days after the visit were left for the herd manager to complete. For analysis, conventional herds were classified as either grazing or nongrazing. Multiple correspondence analysis was used to assess relationships among management factors and selected outcomes for frequency of veterinary usage.

Results—Intensive management practices were closely associated with frequent veterinary usage. Generally, organic management practices were associated with less frequent veterinary usage than were conventional management practices. Conventional grazing practices were associated with intermediate veterinary usage (more than organic practices but less than intensive practices), whereas conventional nongrazing practices were associated with frequent veterinary usage. Cost of routinely scheduled veterinarian visits/45 kg (100 lb) of milk produced/y was greater for small farms than that for large farms.

Conclusions and Clinical Relevance—Results suggested that management intensiveness was more closely associated with frequency of veterinary usage than was organic status; therefore, veterinarians should characterize farms by factors other than organic status when investigating which farms are most likely to use their services. Economic factors substantially affected routine veterinary usage on small farms.

Full access
in Journal of the American Veterinary Medical Association

Summary

Seventy-two lactating dairy cows with left displacement of the abomasum were blindly assigned to treatment by use of the roll-and-toggle procedure or right paralumbar fossa pyloro-omentopexy. All cows were from the same large dairy herd, and survival in the herd and daily milk production were measured for 120 days after treatment. The mean cost was $256.50 for roll-and-toggle cases ($50 for the procedure, $95.70 in milk loss and $110.80 in livestock losses). The mean cost was $406.40 for the pyloro-omentopexy cases ($150 for the procedure, $87.80 in milk loss, and $168.60 in livestock losses). A possible interaction with metritis was discovered, in that pyloro-omentopexy cases cost about $100 more than roll-and-toggle cases when metritis was absent (31 cases) or moderate (32 cases), and cost several times more when metritis was severe (9 cases). Results of the study were in agreement with those of other studies that indicated that the closed repositioning and stabilization techniques are generally less expensive and have comparable results with open repositioning and stabilization techniques. Veterinarians may wish to consider use of this nonsurgical technique for the routine correction of left displacement of the abomasum in dairy cattle.

Free access
in Journal of the American Veterinary Medical Association

Summary

Body condition scoring (using a 5-point scale with quarterpoint divisions) was performed on 66 Holstein dairy cows that began their second or later lactation in August, September, or October 1988. Cows’ body condition was scored beginning on postpartum day 4 (± 1) and subsequently at postpartum days (± 1) 18, 32, 46, 60, 73 and 87. Blood samples were obtained on the same dates. Reproductive health examinations were conducted by 1 of 2 veterinarians beginning at postpartum day 21. Reproductive performance was evaluated in relation to body condition score and serum urea nitrogen and cholesterol concentrations.

Number of days to first recorded signs of estrus and first breeding were not related to body condition score at calving, amount of condition loss, cumulative 80-day milk yield, or 305-day fat corrected milk yield. Cows that calved with body condition score ≥ 3.50 required more days to conceive. Cows losing > 0.75 points of condition had longer days of conception. Body condition score at calving and amount of condition lost were not related to services per conception or diagnosis of follicular cyst.

Cumulative 80-day milk yield was not related to days to conception or services per conception. Cows that produced = the mean 305-day milk yield required more services and had longer days to conception than cows that produced < the mean 305-day milk yield. Cows with diagnosis of ovarian follicular cysts had greater cumulative 80- and 305-day milk yields than did cows that were not diagnosed with follicular cysts.

Cows conceiving with ≤ 2 services did not differ in average daily milk production, body condition score, or serum urea nitrogen concentration from cows conceiving with > 2 services, but cows that conceived with ≤ 2 services had higher serum cholesterol values than did cows requiring more services.

Free access
in American Journal of Veterinary Research

Summary

Body condition scoring (using a 5-point scale with quarter-point divisions) was performed on 66 Holstein dairy cows that began their second or later lactation in August, September, or October 1988. Body condition was scored, beginning on postpartum day 4(± 1) and subsequently at postpartum days (± 1) 18, 32, 46, 60, 73, and 87. Blood samples were obtained on the same dates. Kilograms of milk produced per cow was measured daily. Body condition score and changes in body condition score were evaluated in relation to daily milk production, cumulative 80- day milk yield, and serum urea nitrogen and cholesterol concentrations.

Average daily milk production during week 1 was indicative of cumulative 80-day production, but not of 305- day milk yields. Cows that calved with body condition score ≥ 3.50 did not differ in average daily milk production, cumulative 80-day milk yield, or 305-day milk yield, compared with cows that calved with body condition score < 3.50. Cows that calved with body condition score ≥ 3.50 lost more condition than did cows that calved with body condition score < 3.50. Body condition score at calving and amount of body condition loss interacted with the rate of change in daily milk production.

Serum urea nitrogen concentration did not differ for cows grouped by cumulative 80-day milk production or for cows grouped by amount of condition loss. Serum cholesterol values were higher than previously reported values and increased directly with milk production. Serum cholesterol values were inversely related to condition loss, but changes in cholesterol concentration were not related to condition loss.

Free access
in American Journal of Veterinary Research