We investigated the ability of an antibody-specific, O antigen-based ELISA to document Salmonella typhimurium herd infections by screening of milk samples. Three cattle populations, 20 herds with no history of salmonellosis, 8 herds with history of S. typhimurium episodes within the previous 7 months, and 220 herds of unknown disease status, were tested. A herd was considered ELISA positive if at least 5% of the cows had OD values > 0.3. Among the 20 herds without history of salmonellosis, only 2 herds were ELISA positive, whereas all 8 herds with a known history of salmonellosis were ELISA positive (herd specificity, 0.9 and herd sensitivity, 1.0). A significant correlation (P < 0.001) was found between the OD values of serum and milk samples from cows in the herds with a history of salmonellosis. It was concluded that ELISA testing of individual milk samples can be used for surveillance of herds for S. typhimurium infections, but further modifications are needed to test bulk tank milk samples.

A study was conducted to develop valid estimates of lymphocyte count (LC; cells per microliter) of individual, clinically normal dairy cattle. Estimated weighted regression was used on repeated measures of individual LC to examine 6 models predicting LC as a function of age in cattle not infected with bovine leukemia virus. The generalized growth curve model of analysis of variance was used to estimate intercepts, slopes, and prediction limits for the models and to compare the LC-to-age relationship between Holstein and Guernsey breeds. The best-fitting model (P = 0.0001) with the narrowest prediction interval was LC = 4,414.4 - 84.6X, where X = (age - 48) if age less than or equal to 48 months, and X = 0 if age > 48 months, and 163.6 and 8.1 are the SE of the estimates, respectively. Upper one-sided 95%-predicted normal LC tended to be higher than estimates derived from traditional hematologic keys that use confidence limits of mean LC. Difference was not found in the LC-to-age relationship between the Holstein and Guernsey cattle (P = 0.67). Results of this study provided estimates of normal LC that are more specific in diagnosing lymphocytosis in individual cattle.

Six primiparous Holstein cows were fed a Se-deficient diet, beginning at least 90 days before their first calving, and 6 other primiparous cows were given the same diet plus a supplement of 2 mg of Se/cow/d as sodium selenite. All cows were fed their diets for the duration of the experimental period. One uninfected quarter of each cow was injected with 25 microgram of Escherichia coli endotoxin at postpartum week 5. Leukocytes were isolated by centrifugation from milk collected at postinjection hour 16. Isolated cells were 92 +/- 3% neutrophils and were incubated with Staphylococcus aureus or E coli in a 1:300 ratio. Phagocytosis and intracellular killing by neutrophils were assessed after 0, 30, 60, and 90 minutes by a fluorochrome assay, using acridine orange. Viability of neutrophils was assessed by use of trypan blue. Superoxide anion production and hydrogen peroxide production by neutrophils also were determined. Cows fed Se-deficient diets had significantly (P < 0.05) lower blood Se concentration and blood glutathione peroxidase activity than cows fed Se-supplemented diets. Selenium status had no effect on the phagocytic capacity of neutrophils. Neutrophils obtained from cows fed Se-supplemented diets killed a significantly (P < 0.05) higher percentage of ingested bacteria than did neutrophils from cows fed the Se-deficient diet. Viability was significantly (P < 0.05) reduced by incubation with S aureus in neutrophils from both groups of cows, with neutrophils from Se-deficient cows having lower viability. Superoxide anion production did not differ significantly between neutrophils from the 2 groups, but extracellular hydrogen peroxide concentration was significantly (P < 0.05) higher in neutrophils harvested from milk of cows fed the Se-deficient diet.

Bovine mammary glands were inoculated intracisternally with a streptomycin-resistant (SR) strain of Corynebacterium bovis to determine the number of colony-forming units (CFU) required to induce colonization and to maintain persistence of C bovis colonization throughout lactation and involution. Streptomycin resistance was used as a strain marker. Uninfected quarters in cows during midlactation were challenge exposed with successively higher numbers of SR C bovis until all quarters became colonized. Inoculum containing 790 CFU of SR C bovis established colonization in only 7 of 38 quarters. Colonization persisted in only 4 of these quarters by 23 days after inoculation. Eleven quarters were reinoculated with higher numbers of SR C bovis, and all became colonized by the time challenge-exposure inoculum contained 8 X 10(4) CFU. Colonization persisted throughout the 93-day experimental period. Somatic cell counts were significantly (P less than 0.01) higher in SR C bovis-colonized quarters after inoculation than before. Sixteen additional quarters were inoculated with a mean number of 8 X 10(4) CFU of SR C bovis 7 days before suppression of lactation. All quarters became colonized, and SR C bovis was shed during the experimental period; throughout the nonlactating and peripartum periods, high numbers of SR C bovis in pure culture were shed from 13 of 16 quarters.

An ELISA was developed to detect antibodies to the 41-kd flagellin (P41) of Borrelia burgdorferi in serum obtained from cattle. Absorption studies, immunoblot analysis, immunoelectron microscopy, and correlation of results of the P41-ELISA and the P39-ELISA as well as measurement of the antibody to P41 in calves challenge-exposed with Borrelia theileri were used to assess the specificity of the P41-ELISA. Antigens derived from Escherichia coli, Leptospira interrogans serovar hardjo, and B burgdorferi were used for absorption studies and immunoblot analysis. Antibodies to P41 of B burgdorferi cross-reacted with antigens of E coli, but were not cross-reactive with L hardjo. A value 3 SD higher than the mean of the negative-control population of cattle was defined as the minimum value cutoff value) for a positive result by the P41-ELISA. Use of this value for classification of test results reduced the predicted rate of false-positive results attributable to E coli cross-reactivity to 1%. Immunoblot analysis revealed that test-positive serum from cattle reacted mainly with 41-, 39-, 34-, and 31-kd proteins of B burgdorferi, as well as several smaller proteins. Immunoelectron microscopy revealed that serum from cattle that was test-positive by the P41-ELISA bound to the flagellin and outer membrane of B burgdorferi. Results of absorption studies, immunoblot analysis, and immunoelectron microscopy were correlated and indicated that serum from cattle that was test-positive by P41-ELISA had stronger reactivity to B burgdorferi antigens than to antigens of E coli or L hardjo. The concentrations of antibodies measured by P41-ELISA and P39-ELISA testing were highly correlated [R(2)=0.78]. Calves challenge-exposed with B theileri also had test-positive results by the P-41-ELISA as early as 2 weeks after exposure, but serum antibody concentrations decreased to prechallenge-exposure concentrations by 9 weeks after exposure.

Blood and urine chemical values at parturition in clinically normal Holstein cows (n = 12) were compared with the same values in Holstein cows developing udder edema (n = 12). There was no statistically significant mean difference between the 2 groups for the serum and urine chemical data. Furosemide (500 mg) given IV caused a significant increase in serum calcium and sodium, urine chloride, potassium, and sodium, and fractional excretional ratio of chloride, potassium, and sodium. There was a significant mean decrease in the serum potassium, urine creatinine, osmolality, pH, and specific gravity. Hydrochlorothiazide (250 mg) given IV caused a significant mean increase in serum chloride, urine chloride, potassium, and sodium, and fractional excretion ratio of chloride, potassium, and sodium. There was a significant mean decrease in serum potassium and sodium, urine osmolality, pH, and specific gravity. Acetazolamide (500 mg) given IV caused a significant mean increase in blood urea nitrogen, serum chloride and glucose, urine sodium, and fractional excretion ratio of sodium, while causing a significant mean decrease in serum potassium, sodium, and phosphorus, and urine creatinine. Dextrose (500 g) given IV as a 50% solution caused a statistical mean increase in serum glucose, urine chloride, potassium, and sodium, and fractional excretion ratio of chloride and potassium. A statistical mean decrease occurred in the packed cell volume, blood urea nitrogen, serum calcium, potassium, sodium, and phosphorus, urine creatinine, osmolality, and pH.