Search Results

You are looking at 1 - 10 of 17 items for

  • Author or Editor: Ronald J. Erskine x
  • Refine by Access: All Content x
Clear All Modify Search

SUMMARY

Ten Holstein cows were fed a selenium-deficient (SeD) diet containing 0.04 mg of Se/kg of dry matter for 3 months before and throughout their first lactation. A selenium-supplemented (SeS) group of 10 cows was fed an additional 2 mg of Se/head/d to increase dietary Se concentration of the dry matter to approximately 0.14 mg/kg of body weight. An intracisternal challenge exposure of 40 to 60 colony-forming units (cfu) of Staphylococcus aureus was administered into 1 or 2 quarters of the udder of each trial cow at about the twenty-second week of lactation. Blood Se concentration (μg/ml±sem) at the time of challenge exposure was 0.035±0.002 in SeD and 0.139±0.006 in SeS cows. Infections were established in 14/16 of the challenge-exposed quarters in SeD and 16/19 of the challenge-exposed quarters in SeS cows. The infection in 1 quarter of each Se group cleared without treatment by the end of the 8-week trial period.

Log10 peak bacterial concentrations in milk from infected SeD quarters (5.04±0.25 cfu/ml) were higher (P < 0.05) than those of infected SeS quarters (4.40±0.12 cfu/ml). Log10 peak somatic cell count (scc) in milk from infected SeD quarters (7.18±0.08 cells/ml) did not differ from that of SeS quarters (7.17±0.05 cells/ml). Peak bacterial concentrations were attained sooner (P < 0.05) in SeD quarters (9.5±4.0 days) than in SeS quarters (20.7±3.1 days). Similarly, peak scc were reached earlier (P < 0.05) in SeD (4.3±1.1 days) than in SeS quarters (13.3±3.8 days). The Se groups did not differ significantly with respect to peak milk concentrations of bovine serum albumin or IgGl. Throughout the 8-week trial, the Se groups did not differ significantly in milk bacterial concentration, scc, bovine serum albumin, or IgGl. Selenium status did not affect the percentage of challenge exposures resulting in infection, duration, or severity of experimentally induced S aureus mastitis.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of infection with bovine leukosis virus (BLV) on lymphocyte proliferation and apoptosis in dairy cattle.

Animals—27 adult Holstein cows.

Procedures—Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood from lactating Holstein cows seronegative for BLV (n = 9 cows), seropositive for BLV and aleukemic (aleukemic; 9), and seropositive for BLV and persistently lymphocytotic (PL; 9). Isolated PBMCs were assayed for mitogen-induced proliferation and were analyzed by means of flow cytometry. The PBMCs from a subset of each group were assayed for apoptosis, caspase-9 activity, and expression of selected genes related to apoptosis.

Results—PL cows had significantly higher total lymphocyte counts and significantly lower proportions of T-lymphocyte populations than did BLV-negative and aleukemic cows. Both groups of BLV-infected cows had significantly higher proportions of B cells and major histocompatibility complex II–expressing cells than did BLV-negative cows. Proliferation with concanavalin A was significantly lower for PL cows, compared with proliferation for BLV-negative cows. Pokeweed mitogen–induced proliferation was significantly higher for aleukemic and PL cows than for BLV-negative cows. Gene expression of apoptosis-inhibitory proteins BCL2 and BCL2L1 was significantly higher for aleukemic cows and expression of BCL2 was significantly higher for PL cows than for BLV-negative cows.

Conclusions and Clinical Relevance—Cattle infected with BLV had marked changes in PBMC populations accompanied by alterations in proliferation and apoptosis mechanisms. Because the relative distribution and function of lymphocyte populations are critical for immune competence, additional studies are needed to investigate the ability of BLV-infected cattle to respond to infectious challenge.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of bovine leukemia virus (BLV) infection on absolute neutrophil and lymphocyte concentrations in healthy lactating Holstein dairy cattle.

Design—Observational cross-sectional survey.

Animals—311 healthy lactating Holstein dairy cattle from herds in Michigan (n = 2), Wisconsin (1), Iowa (1), and Pennsylvania (1).

Procedures—Whole and anticoagulated (EDTA) blood samples were collected. Serum samples were tested for antibody against BLV by use of an ELISA. Absolute neutrophil and lymphocyte concentrations were measured in EDTA blood samples with an automated hematology analyzer and manual differential cell counts.

Results—208 cows tested positive and 103 cows tested negative for anti-BLV antibodies. Neutrophil concentration was not significantly different between BLV-positive versus BLV-negative cattle. The distribution of lymphocyte concentration was positively skewed for the entire cow population (n = 311) and the BLV-positive subset (208). In contrast, lymphocyte concentration distribution was approximately normal for BLV-negative cows (n = 103). Consequently, the presence or absence of BLV infection strongly influenced the calculated neutrophil-to-lymphocyte concentration ratio.

Conclusions and Clinical Relevance—Results indicated that absolute lymphocyte concentration is significantly affected by BLV infection in dairy cattle. Accordingly, hematologic reference intervals should be derived from healthy animals that are not infected with BLV and patient BLV status must be considered for meaningful interpretation of lymphocyte concentration. We recommend that the calculated neutrophil-to-lymphocyte ratio be abandoned because it does not provide more information than direct comparison of patient absolute leukocyte concentration with updated reference intervals from healthy BLV-negative cattle.

Full access
in Journal of the American Veterinary Medical Association

Objective—

To determine the effect of administration of vitamin E (D-α-tocopherol) on the incidence of retained placenta, metritis, and clinical mastitis during early lactation and on tocopherol concentrations.

Design—

Prospective randomized controlled study.

Animals—

420 Holstein cows

Procedure—

Vitamin E (3,000 mg, IM, once) was administered to 204 cows 8 to 14 days before expected parturition, and 216 control cows were not treated. The number of cows that had retained placenta, metritis, clinical mastitis, displaced abomasum, and clinically apparent acetonemia or hypocalcemia were recorded. Serum concentrations of tocopherol, the tocopherol:cholesterol ratio, and glutathione-peroxidase activity were determined from samples obtained before administration of vitamin E, 7 and 14 days after administration, and at 30 days after parturition from 36 treated and 36 control cows.

Results—

Administration of vitamin E significantly decreased the incidence of retained placenta and metritis (13/204 [6.4%] and 8/204 [3.9%], respectively, for the vitamin E-treated group; 27/216 [12.5%] and 19/216 [8.8%], respectively, for the untreated group) but did not affect the incidence of clinical mastitis. Serum vitamin E concentration was significantly higher in treated than in control cattle at 7 and 14 days after administration, but serum tocopherohcholesterol ratio was significantly higher only at 7 days after administration.

Clinical Implications—

Parenteral administration of a single injection of vitamin E before parturition may decrease the incidence of retained placenta and metritis in dairy cows but will increase serum concentrations for 7 to 14 days after administration. (J Am Vet Med Assoc 1997;211:466–469)

Free access
in Journal of the American Veterinary Medical Association

Summary

Supplementation of selenium and vitamin E to enhance disease resistance in dairy cattle has become common, particularly to prevent periparturient reproductive disorders and mastitis. To establish reference values for serum vitamin E and selenium concentrations in postparturient dairy cattle and to determine whether serum concentrations of these micronutrients varied with season and stage of lactation, cows from a stratified random sample of 50 herds were studied for 1 year. Blood samples were collected from each of the 50 study herds twice, from the 10 most recently parturient cows or from 10% of the herd, whichever was greatest. Mean concentration of vitamin E and selenium was 2.55 μg/ml and 78.12 ng/ml, respectively. Vitamin E concentrations were significantly (P < 0.05) higher during the summer and fall than during the winter and spring. Selenium concentrations were significantly (P < 0.05) lower during the summer and fall than during the winter and spring. Herd, season of blood sample collection, and time since parturition were significant (P < 0.02) in explaining variation in vitamin E and selenium concentrations.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effect of hyperimmunization with an Escherichia coli J5 bacterin on serum IgG2 concentration, incidence of clinical mastitis, and rate of survival to the end of the lactation period (ie, day 305) in adult lactating dairy cattle.

Design—Randomized controlled trial.

Animals—1,012 Holstein cows in their second lactation and greater.

Procedures—All cows were given 3 doses of the J5 bacterin; cows in the hyperimmunization group were given an additional 3 doses during the first 3 months of lactation. Blood was collected from a small sample of cows to determine anti-J5 IgG2 concentrations.

Results—Cows in the hyperimmunization group had higher mean serum anti-J5 IgG2 concentrations than did control cows 28 days after administration of the fourth, fifth, and sixth doses of the J5 bacterin. However, mean serum anti-J5 concentrations during the subsequent lactation were not significantly different between groups. The proportions of cows that developed clinical mastitis were not significantly different between groups. However, control cows were more likely to have severe clinical mastitis than were cows in the hyperimmunization group. The percentage of control cows that remained in the herd to day 305 was significantly lower than the percentage of cows in the hyperimmunization group that did.

Conclusions and Clinical Relevance—Results suggested that hyperimmunization of mature lactating dairy cattle was associated with increased serum anti-J5 IgG2 concentrations and decreased incidence of severe clinical mastitis, but did not alter survival rate of cows that developed severe clinical mastitis.

Full access
in Journal of the American Veterinary Medical Association

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.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the likelihood of false-positive results when testing milk samples from individual cows by use of 3 commercially available assays (Penzyme Milk Test and the SNAP β-lactamand Delvo- SP assays) labeled for use with commingled milk.

Sample Population—Milk samples from 111 cows with mild clinical mastitis.

Procedure—Cows were randomly assigned to the control (no antimicrobials) or intramammary treatment group. Posttreatment milk samples were collected at the first milking after the labeled withholding period or an equivalent time for controls, randomly ordered, and tested twice by use of each assay and once by use of high-performance liquid chromatography. Sensitivity, specificity, and positive and negative predictive values were determined for each assay. Concordance of results for the same sample was assessed for each assay by calculating κ.

Results—Sensitivities of the Delvo-SP and SNAP β-lactam assays were > 90%, whereas the sensitivity of the Penzyme Milk Test was 60%. Positive predictive values (range, 39.29 to 73.68%) were poor for all 3 assays. Concordance of test results was excellent for the SNAP β-lactam and Delvo-SP assays (κ = 0.846 and 0.813, respectively) but was less for the Penzyme Milk Test (κ = 0.545).

Conclusions and Clinical Relevance—Because of the low positive predictive values, these 3 assays may not be useful for detecting violative antimicrobial residues in individual milk samples from cows treated for mild clinical mastitis. However, repeatability of each assay was considered good to excellent. (Am J Vet Res 2001;62:1716–1720)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of injection site on antibody response to J5 Escherichia coli bacterin.

Animals—28 adult Holstein cows.

Procedures—Cows were randomly assigned as control cattle (n=4cows), not administered J5 E coli bacterin; 3X (8), administered 3 doses of bacterin SC in the left side of the neck; 5XN (8), administered 5 doses of bacterin SC in the left side of the neck; or 5XSR (8), administered 5 doses of bacterin SC sequentially in the left side of the neck, right side of the neck, right side of the thorax, left side of the thorax, and left side of the neck. Blood samples were collected from the cows to determine anti-J5 E coli IgG1 and IgG2 concentrations.

Results—Vaccinated cows had higher mean serum anti-J5 E coli IgG1 concentrations than did control cows. The 5XN and 5XSR cows had higher mean serum anti-J5 E coli IgG1 concentrations than did 3X cows. Additionally, 5XSR cows had higher mean serum anti-J5 E coli IgG1 concentrations than did 5XN cows. Vaccinated cows had higher mean serum anti-J5 E coli IgG2 concentrations than did control cows. The 5XN and 5XSR cows had higher mean serum anti-J5 E coli IgG2 concentrations than did 3X cows. The 5XSR cows had higher mean serum anti-J5 E coli IgG2 concentrations than did all other groups at 84 days after the fifth vaccination.

Conclusions and Clinical Relevance—Sequential doses of core-antigen bacterins administered at different anatomic locations may improve antibody response in dairy cattle.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine and compare levels and patterns of antimicrobial resistance among Escherichia coli isolated from pigs on farms that did not use antimicrobial agents versus pigs produced under conventional methods.

Design—Cross-sectional study.

Sample Population—35 antimicrobial-free and 60 conventional swine farms.

Procedures—Farms were visited once, and fecal samples were collected from 15 finisher pigs if available. One E coli isolate from each sample was tested for susceptibility pattern to 14 antimicrobial agents by use of microbroth dilution.

ResultsE coli isolates were recovered from 1,381 (97.1%) of 1,422 fecal samples. Herd size was significantly larger for conventional swine farms. Resistance to ceftriaxone, ciprofloxacin, or nalidixic acid was not observed on any of the 95 farms. Three isolates from 2 conventional farms were resistant to ceftiofur. Conventional farms had significantly higher levels of resistance to ampicillin, sulfamethoxazole, tetracycline, and chloramphenicol, compared with antimicrobial-free farms. Fourteen percent of E coli isolates were susceptible or had intermediate resistance to all the tested antimicrobial agents. The 3 most frequent patterns of multiple resistance were streptomycin-tetracycline, sulfamethoxazole-tetracycline, and kanamycin-streptomycin-sulfamethoxazole-tetracycline.

Conclusions and Clinical Relevance—Cessation of antimicrobial use did not appear to result in an immediate reduction in antimicrobial resistance in swine farms. Prospective studies of long-term antimicrobial usage and cessation are needed to estimate the extent to which food animal production may be contributing to antimicrobial drug resistance and might provide a direct measure of the rates of reversibility of antimicrobial drug resistance that might be achieved by curtailing antimicrobial usage.

Full access
in Journal of the American Veterinary Medical Association