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A stratified random sample of 50 Ohio dairy herds, monitored for 1 year between March 1988 and May 1989, was used to estimate the component costs of clinical mastitis per cow-year overall and by organism, the component costs of an episode of clinical mastitis overall and by organism, and the incidence of clinical mastitis by organism. Each herd was visited monthly by a veterinarian who conducted on-farm interviews and completed standardized data-collection forms designed to elicit economic information about the on-farm costs of clinical mastitis and mastitis prevention. Producers collected milk samples prior to treatment of clinical mastitis cases. Culturing methods allowed identification of 18 specific mastitis pathogen classifications. Annual costs estimated were on a per cow-year and clinical episode basis. The monthly mean population of cows monitored was 4,068. Mastitis prevention cost $14.50/cow-year, whereas the cost incurred by producers because of clinical cases of mastitis was $37.91. Organisms prevalent in the cows' environment caused the most costly types of mastitis. Disregarding contaminated samples and episodes for which no milk samples were taken, mastitis for which 2 organisms were isolated accounted for 35.5% of costs of clinical mastitis, followed by cases for which Escherichia coli (21.3%) was isolated, cases for which culturing yielded no growth (8.6%), and cases for which esculin-positive Streptococcus spp (6.4%), Klebsiella spp (5.7%), esculin-negative CAMP-negative Streptococcus spp (5.1%), Enterobacter spp (4.8%), coagulase-negative Staphylococcus spp (4.1%), coagulase-positive Staphylococcus spp (3.0%), S agalactiae (2.5%), and Bacillus spp (1.2%) were isolated.(ABSTRACT TRUNCATED AT 250 WORDS)

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A cross-sectional study of 1,032 dairy herds in Ohio was conducted to determine the prevalence of the major contagious pathogens of mastitis (Streptococcus agalactiae and Staphylococcus aureus) and the use of common mastitis control measures. Herd owners were surveyed by mail concerning their use of mastitis control measures. The survey focused on treatment of nonlactating cows, postmilking teat dipping, culling practices, milking machine maintenance, treatment for clinical mastitis, and premilking hygiene practices. Nearly 90% of questionnaires were returned. The prevalence of Streptococcus agalactiae and Staphylococcus aureus was determined by use of bulk-tank milk samples. Most herds (n = 802) met the criteria for classification into 1 of 4 groups: (1) Free of contagious pathogens, as determined by inability to isolate coagulase positive staphylococci (CPS) and esculin-negative CAMP positive streptococci (ENCPS) from 3 bulk-tank milk samples, (2) CPS, but not ENCPS, isolated from at least 1 sample, (3) ENCPS, but not CPS, isolated from at least 1 sample, (4) both ENCPS and CPS isolated from at least 1 sample. The number of herds in which both ENCPS and CPS were isolated was low; therefore, these herds were grouped with herds in which ENCPS alone was isolated for the evaluation of mastitis control practices related to herd pathogen status. Herd somatic cell count (SCC) was determined using Dairy Herd Improvement Association data by calculating the geometric mean SCC from individual cow test day SCC. Twelve months of SCC data from 741 herds were included in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

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Forty-eight herds participating in the 1988/1989 Ohio National Animal Health Monitoring System dairy project were monitored for 1 year to determine the effects of environment and management on mortality in preweaned calves. Environmental factors were evaluated by veterinarians during monthly visits to the herds. Management procedures were measured through the use of a questionnaire administered near the end of the project. Mortality in preweaned calves was calculated for each herd by using data from project records on calf mortality and animal inventory, which were collected monthly by veterinarians. Relationships between the management/environment variables and calf mortality were examined by use of analysis of covariance. Herd size, days on a nipple feeder, navel disinfection, type of housing, and whether each calf observed with diarrhea was treated with antibiotics were the variables that had an impact on herd mortality. These variables explained approximately 39% of the variation in mortality among herds.

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Dairy herds in Ohio were selected by stratified random sampling for participation in a disease-monitoring study to relate Streptococcus agalactiae intramammary prevalence to herd management and environmental conditions. Of 48 herds studied, 27 herds had at least 1 cow infected with this pathogen. Management and environmental conditions were assessed by direct observation as well as by an interview with the dairy producers. One-way ANOVA or chi 2 analysis, with presence or absence of Streptococcus agalactiae as the dependent variable, was used to test each of 70 independent variables. Variables found significant at P less than 0.20 were further evaluated by use of logistic regression. Our sample size permitted only 4 independent variables to be simultaneously evaluated by logistic regression. The most predictive risk factors were identified as poor teat and udder hygiene, poor environmental sanitation, large herd population, and use of a shared washcloth for premilking cleaning of teats and udders.

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To estimate herd prevalence of Salmonella spp, fecal specimens were obtained for culture from neonatal calves of 47 Ohio dairy herds. Of the 452 calves tested, 10 calves from 7 farms were culture-positive. Salmonella serotypes isolated were S dublin, S typhimurium, S enteritidis, S agona, S mbandaka, and S montevideo. Bulk tank milk filters from these dairies were also submitted for culture. Salmonella sp was isolated from 1 of the 50 filters, and 2 calves from this herd were found to be shedding Salmonella sp of the same serotype.

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Forty-eight dairy herds in Ohio were selected as a stratified random sample for participation in a disease monitoring study to relate the prevalence of IMI with coliform and environmental streptococci to herd management and environmental conditions. Management and environmental conditions were assessed by farm inspection and by an interview with the dairy producers. A separate analysis for each independent variable identified many potential disease determinants. A multivariable analysis of a covariance model to predict the prevalence of coliforms had 6 model df (R2 = .47). Increased prevalence of coliform infection was associated with an increased amount of milk remaining in the udder after milking, use of free stalls, regular use of a running water wash, increased person hours per cow spent milking, and poor sanitation. The multivariable model for environmental streptococci used 5 model df (R2 = .51). Increased prevalence of environmental streptococci was associated with poor sanitation, increased number of days dry, use of tie stalls, no use of a shared wash cloth, and no use of an individual dry cloth.

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The purpose of this study was to document the effect of calfhood vaccination for Mycobacterium paratuberculosis on a serologic ELISA. Fifteen calves vaccinated with a killed paratuberculosis vaccine and 5 unvaccinated control calves were tested from the first through the fifteenth month of life. Age of vaccination ranged from 5 to 40 days. Blood samples were collected prior to vaccination and periodically thereafter. Serum antibody was analyzed by use of the ELISA. All calves were ELISA-negative prior to vaccination. Thirteen of 15 vaccinated calves became ELISA-positive between 2 and 6 months after vaccination. The unvaccinated cohort remained ELISA-negative. Wide-spread use of vaccine may interfere with diagnosis of paratuberculosis and with control programs that are based on serologic tests that measure humoral antibody.

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Cows with three hundred and sixteen cases of clinical mastitis were sampled by microbiologic culture during a 6-mo period on a 1700-cow Michigan Holstein dairy farm. Daily milk weights were obtained on all cows before clinical onset and for 60 d after onset. Predicted post-mastitis production, projected on the basis of premastitis production and the lactation curves of contemporary non-mastitic herdmates, was compared with actual daily milk production during the 60 d following clinical onset. Cows experiencing clinical mastitis produced approximately 341 kg less salable milk during the 60 d after clinical onset compared with projected production. This milk loss included both decreased production and milk withheld from market following antibiotic treatment. Pluriparous cows lost 2.06 times as much milk as first lactation cows, and cows with mastitis occurring before 150 d in lactation lost 1.40 times as much milk when compared with other cows. Cows with mastitis occurring in the winter showed a milk loss 1.37 times greater than cows with mastitis in summer. The identity of the mastitis agent isolated from the clinical case was not strongly associated with the drop in milk production in the 60 d following clinical onset.

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A dot ELISA was developed for detection of antibodies to Mycobacterium paratuberculosis. The assay was evaluated by testing sera from cattle that were determined, by bacteriologic culturing of feces, to be infected with M paratuberculosis and were suspected of having clinical disease. Further evaluation involved testing sera from cattle in which M paratuberculosis had not been isolated from feces on several attempts. Results of the dot ELISA were positive for sera from 86 of 101 infected cattle, and results were negative for sera from 64 of 64 noninfected cattle. Results of conventional ELISA and agar gel immunodiffusion (AGID) tests were positive for 79 of 99 and for 51 of 101 infected cattle, respectively. The dot ELISA also was evaluated by comparing results of testing 708 sera with results of bacteriologic culturing of matched fecal samples from 262 cattle in 3 central Ohio dairy herds known to include cattle infected with M paratuberculosis. Results of the dot ELISA were positive for 25 of 39 sera from cattle with positive results on culturing of concurrently obtained fecal specimens. The dot ELISA results were negative for 661 of 669 sera from cattle with negative results to culturing of concurrently obtained fecal specimens. The 39 sera from cattle with positive results on bacteriologic culturing of matched fecal specimens had positive results for ELISA and the AGID test 25 and 14 times, respectively. The 669 sera from cattle with concurrently negative results on bacteriologic culturing of feces had negative results to ELISA and the AGID test 559 and 668 times, respectively.

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Nine commercial dairy herds, each with low herd milk somatic cell counts, were monitored for 1 yr to determine prevalence of intramammary infections and rates of clinical mastitis. Staphylococcus species was the bacterial group most frequently isolated from quarters at calving and at drying off. Environmental streptococci and coliform intramammary infections totaled less than 6% of quarters at both calving and at drying off. Staphylococcus aureus were isolated from less than 1% of quarters and Streptococcus agalactiae from 0% of quarters at both calving and drying off. A total of 646 clinical cases of mastitis were diagnosed in 548 quarters of 406 cows. Mean rate of clinical mastitis among herds was .457 clinical cases/305 cow-days. Rates of clinical mastitis ranged among herds from .273 to .748 clinical cases/305 cow-days. Coliforms and bacteriologically negative and environmental streptococci accounted for 82.3% of clinical cases. Rates of clinical mastitis and severity of clinical signs differed among herds, seasons of the year, parity groups, and stages of lactation. Rates of clinical mastitis were highest during summer, in first lactation cows, and during the first 7 d of lactation.

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In utero transmission of Mycobacterium paratuberculosis, the causative agent of paratuberculosis in cattle, has been suggested. Tissue specimens were obtained at a packing plant from pregnant dairy cows and their fetuses and from cows with clinical signs of paratuberculosis and from their fetuses. Specimens were processed according to methods described for isolating M paratuberculosis from bovine tissues and were incubated on Herrold egg yolk medium for 16 weeks. Presumed positive specimens were confirmed to be M paratuberculosis, using acid-fast staining and subculturing. Of 407 lymph nodes from cows, 34 (8.4%) were culture positive for M paratuberculosis; 9 of 34 (26.4%) of these culture-positive cows had fetuses from which specimens were also culture positive. The results estimated the risk of fetal infection with M paratuberculosis to be 26.4% (95% confidence interval between 11.3 and 40.7%).

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Bacterial counts were monitored for 1 yr in bedding materials used on nine commercial dairies. Organic materials used to bed lactating cows had significantly higher moisture content and gram-negative bacterial, coliform, Klebsiella species, and streptococcal counts than did inorganic materials. Klebsiella species counts were higher in sawdust than in chopped straw. Streptococcal counts were higher in chopped straw than sawdust. Bacterial counts did not differ between sand and crushed limestone. Gram-negative bacterial and coliform counts were higher during summer and fall than in winter and spring months. Streptococcal counts did not differ among seasons of the year. Linear relationships were significant between total rates of clinical mastitis during lactation and both gram-negative bacterial and Klebsiella species counts in lactating cow bedding. These data indicate that bacterial populations differed between both types of bedding and among seasons of the year. Rates of clinical mastitis were related to bacterial counts in bedding.

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Factors associated with bulk tank milk bacterial and somatic cell counts were investigated for one year on nine well managed dairies. Geometric mean total bacterial count among dairies was 4.4 × 103 colony cfu/ml. Geometric mean bulk tank milk somatic cell counts among herds was 265 × 103ml. Bacterial counts in bulk tank milk were correlated with rates of coliform and environmental streptococcal clinical mastitis cases. Rates of total clinical cases were also correlated with bulk tank milk somatic cell counts. Correlations were measured among bulk tank milk bacterial counts and gram-negative bacterial, coliform, Klebsiella species, and streptococcal counts in materials used to bed lactating cows. Total bacterial and staphylococcal bulk tank milk counts increased when synthetic rubber liners were used greater than 800 quarter milkings. Correlations measured indicated that monitoring bulk tank milk may be an effective means of detecting management changes in herds with low bacterial and milk somatic cell counts.

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Dairy replacement heifers given two strategic treatments with ivermectin (0.2 mg/kg) three and eight weeks after turnout to spring pastures in northern USA had mean adjusted weight gains (62.3 kg) that were 62 per cent (P less than 0.02) greater than those of control heifers (38.5 kg) at the time of winter housing. Pasture infectivity was consistently higher in control pastures and there was a sixfold difference between treatment (56 L3/kg) and control (358 L3/kg) pastures by the time of winter housing on October 18. This study confirmed earlier studies in northern USA demonstrating the value of two strategic treatments in achieving significant increases in weight gains and hastening the time of first breeding by one to three months at a saving of $40 to $140 per heifer. It was concluded that this dosing strategy is a satisfactory method of parasite control for dairy replacement heifers in northern USA without undue selection for drug resistance.

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The reporting of herd summaries of individual cow somatic cell counts differs between the nine Dairy Records Processing Centers. The objectives of this paper are to review the present reporting; to compare the methods used to calculate herd somatic cell counts; and to discuss the epidemiologic implications of these methods. Estimates of central tendency and frequency distributions are the most commonly used herd summary statistics for somatic cell counts. Analyses of the frequency distributions are less widely available. Potential uses of herd somatic cell counts are to measure one aspect of herd milk quality; to estimate the prevalence of mastitis; to analyze mastitis patterns within the herd; and to investigate new areas for mastitis control research. Presently, the best available methods for these applications appear to be bulk tank somatic cell counts or weighted arithmetic means for gauging milk quality; frequency distributions for estimating mastitis prevalence; analyses of frequency distributions of mean linear score by lactation and stage of lactation for identifying mastitis patterns within a herd; and frequency distributions or estimated incidence rates, adjusted for differences in age and stage of lactation, for investigating new areas for mastitis control research.

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The characterization of a purified antigen from Mycobacterium paratuberculosis, recently made commercially available for use in serodiagnosis by enzyme-linked immunosorbent assay (ELISA), of paratuberculosis in cattle was described. This assay had 89% specificity and 83% sensitivity for M paratuberculosis infection. The protein/polypeptide composition of the purified antigen was compared with that of a crude protoplasmic extract of strain 18 M paratuberculosis used in the agar-gel immunodiffusion test and ELISA and with that of sonicated strain 19698 M paratuberculosis organisms grown on Dorset-Henley synthetic liquid medium. The sonicated M paratuberculosis contained 27 major proteins/polypeptides; the crude protoplasmic extract, 18; and the purified antigen contained 14 proteins/polypeptides, using sodium dodecyl-sulfate polyacrylamide-gel electrophoresis analysis. The serologic reactivity of these proteins/polypeptides were defined, using the enzyme-linked immuno-electrotransfer blot technique. The sonicated M paratuberculosis contained 20 serologically reactive proteins/polypeptides (34,000 to 84,000 daltons); the crude protoplasmic extract contained 3 (37,000 to 45,000 daltons); and the purified extract contained a diffuse polypeptide band (34,000 to 38,000 daltons). Identification by enzyme-linked immuno-electrotransfer blot technique of M paratuberculosis antigens reactive in the ELISA will allow us to further study these antigens in the ELISA to improve sensitivity and specificity of the diagnostic test.

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