Summary 152 quarter milk samples were subjected to microbiological examination in the fresh state and after frozen storage for 7 and 14 days at — 80°C. It was found that milk samples can be preserved at — 80°C for 14 days without any change in the number of bacterially positive quarter milk samples (86), but with a reduction in the number of streptococcal isolates. Loss of streptococcal isolates did not reduce the number of positive samples because in those samples from which a streptococcus isolate was lost after freezing, a staphylococcus or Escherichia coli persisted. Another 158 composite milk samples were microbiologically examined for isolation of streptococci in the fresh state and after frozen storage for 7 and 14 days at —70°C; a similar reduction in streptococcal isolates occurred. Zusammenfassung Die Wirkung des Einfrierens von Milchproben auf die kulturellen Ergebnisse 152 Viertelgemelksproben wurden in frischem Zustand und nach Aufbewahrung in gefrorenem Zustand bei — 80°C uber sieben und vierzehn Tage einer mikrobiologischen Untersuchung unterzogen. Es wurde festgestellt, das Milchproben bei sehr niedrigen Temperaturen (— 80°C) fur eine Zeit von 14 Tagen ohne Anderung der Anzahl bakteriologisch positiver Viertelgemelksproben, aber mit einer Reduktion der Anzahl der Streptokokken-Isolate konserviert werden konnen. In dieser Arbeit reduzierte der Verlust von Streptokokkenisolaten nicht die Anzahl positiver Milchproben, weil in jenen Milchproben, in denen Streptokokken nach dem Einfrieren nicht mehr nachgewiesen werden konnten, Staphylokokken oder Escherichia coli uberlebten. Weitere 158 zusammengesetzte Milchproben wurden zum Nachweis von Streptokokken im frischen Zustand und nach Tiefgefrieren wahrend 7 und 14 Tagen bei einer Temperatur von — 70°C mikrobiologisch untersucht; eine ahnliche Abnahme der Streptokokken-Nachweise wurde beobachtet. Resume Action de la congelation de echantillons de lait sur les resultats des examens microbiologiques 152 echantillons de quartiers ont subi un examen microbiologique a l'etat fais et apres une congelation a — 80°C durant 6 et 14 jours. Il a ete etabli que les echantillons de lait n'ont pas montre de modification sur le nombre des echantillons bacteriologiquement positifs apres une periode de 14 jours a — 80°C; il n'y a eu qu'une reduction du nombre des isolements de streptocoques. La perte des isolements de streptocoques n'a pas diminue dans ce travail le nombre des echantillons positifs car des staphylocoques et E. coli ont survecu dans chaque prelevement de lait pour lesquels la congelation avait empeche l'isolement de streptocoques. On a examine en plus 158 echantillons de lait frais et congele durant 7 et 14 jours a — 70°C afin de determiner la presence de streptocoques; une diminution semblable des isolements de streptocoques a ete observee. Resumen El efecto de la congelacion de las muestras de leche sobre los resultados culturales 152 muestras de leche de cuarterones se sometieron al estado fresco a un examen microbiologico y a otro tras conservacion al estado congelado a — 80°C a lo largo de siete y catorce dias. Se comprobo que las muestras de leche se pueden conservar a temperaturas muy bajas (— 80°C) por un tiempo de 14 dias sin variacion de la cantidad de muestras de ordeno de cuarterones bacteriologicamente positivas, aunque habia que contar con la reduccion de la cifra de los aislamiento de estreptococos. En este trabajo no reducia la perdida de aislamientos de estreptococos la cifra de muestras positivas de leche, porque en aquellas muestras de leche en que ya no se podian identificar estroptococos despues de la congelacion sobrevivian estafilococos o Escherichia coli. Se examinaron microbiologicamente otras 158 muestras compuestas de leche para identificar estreptococos al estado fresco y despues de la congelacion profunda durante siete y catorce dias a la temperatura de — 70°C; se observo una disminucion semejante de las identificaciones de estreptococos.

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)

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)

A stratified random sample of Ohio dairy herds was studied to relate herd management and environmental conditions to intramammary infection with coagulase-positive staphylococci. Management and environmental conditions were assessed by investigator observation and by interview with the diary producers. Separate analyses for each of 70 management and environmental independent variables identified many potential disease determinants. A logistic regression model used five model degrees of freedom to predict the prevalence of coagulase-positive staphylococci in more than 1% of quarters. Increased risk of infection with coagulase-positive staphylococci was associated with dirty udders, high-line milking systems, and less crowded housing conditions. Decreased risk of infection was associated with a herd size of 50–100 cows.

A stratified-random sample of 48 Ohio dairy herds participated in a 1-year disease monitoring survey to study herd management and environmental conditions affecting udder infection and clinical mastitis incidence. The mean monthly bulk-tank somatic cell count was used as an indicator of overall udder infection. Clinical incidence was determined by monthly on-farm interviews with the dairy producers. Management and environmental conditions were assessed by direct observation as well as by personal interview of dairy managers. The final multivariable analysis-of-variance model of log bulk-tank somatic cell count had an R2 value of 0.43. Lower log bulk-tank somatic cell count was found in herds with hired milkers, a clean and dry cow exercise area, clean teats following milking and fewer milking cows. The number of months spent on pasture was also significant. The final model for clinical mastitis incidence had an R2 value of 0.38. Less clinical mastitis was found on farms where straw bedding was used, pre-dip was not used, where there were fewer cows, fewer person-hours per cow were spent milking cows, a greater percentage of calvings occurred in the designated calving facility, and cows spent fewer months per year on pasture. Other potentially important disease determinants could not be included in the final models because of limited sample size relative to the model degrees of freedom (six each).

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.

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.

Fifty Ohio dairy farms selected by stratified random sample were monitored to determine the incidence rate of clinical mastitis and prevalence of intramammary infection with the major intramammary pathogens. Population parameters for clinical mastitis incidence rate were estimated as 2.19, 3.33 and 4.36 cases per 100 cow-months at risk for herds with less than 50 cows, herds with 50–99 cows, and herds with more than 99 cows, respectively. The most common isolates from clinical cases were coagulase-negative staphylococci and Escherichia coli, each present in 14.6% of samples taken. Estimates of population prevalence of intramammary infection for Ohio dairy farms were: coagulase-positive staphylococci, 2%; coagulase-negative staphylococci, 2%; E. coli, 1%; other coliforms, 1%; Streptococcus agalactiae, 2%; esculin-positive streptococci, 5%; other esculin-negative streptococci, 3%.

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.

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.

Nine dairy herds (mean size, 149 cows) with bulk-tank milk somatic cell counts of less than 300,000 cells/ml and greater than 80% of cows with Dairy Herd Improvement Association linear somatic cell counts less than or equal to 4 were selected for study. Each herd was monitored for 12 consecutive months. Duplicate quarter-milk specimens were collected from each cow for bacteriologic culturing at beginning of lactation, cessation of lactation, and at the time of each clinical episode of mastitis. Streptococcus agalactiae was never isolated and Staphylococcus aureus was isolated from less than 1% of all quarters. There were 554 episodes of clinical mastitis. During the year of study, the incidence rate of clinical mastitis varied from 15.6 to 63.7% of cows among the 9 herds. Mean costs per cow per year in herd for mastitis prevention were: $10 for paper towels, $3 for nonlactating cow treatment, and $10 for teat disinfectants. Mean cost associated with clinical mastitis was $107/episode. Approximately 84% ($90) of the costs attributed to a clinical episode were associated with decreased milk production and nonsalable milk. Costs of medication and professional veterinary fees per clinical episode varied significantly among the 9 herds. Three of the herds did not have a veterinarian treat a clinical episode of mastitis during the year of study even though 2 of these herds had the first and third highest incidence rates of clinical mastitis. When calculated on a per cow in herd basis, mean costs of $40/cow/year were attributed to clinical mastitis.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of a single bulk tank milk culture and a single milk filter culture was studied for their suitability as screening tests for coagulase-positive staphylococci and Streptococcus agalactiae . Bulk tank and bulk tank milk filter cultures were compared to quarter milk cultures taken from individual cows at 49 Ohio dairy herds selected from all Ohio dairy herds by a stratified random sampling scheme. Individual cow quarter milk samples were collected from a sample of all milking cows using a sampling scheme designed to detect an organism present in 2% of quarters, with 95% confidence intervals between 1 and 3%. Seventeen (35%) herds had one or more cows positive for S. agalactiae and 34 (69%) had one or more cows positive for coagulase-positive staphylococci. Using the results of individual cow sampling as the standard, the sensitivity for S. agalactiae was estimated as 23.5% for a single milk filter sample and 35.3% for a single bulk tank milk sample. The sensitivity for coagulase-positive staphylococci was estimated as 52.9% for a single milk filter culture and 41.2% for a single bulk tank milk culture. Based on these results and those of others, it appears that a single bulk tank or milk filter sample has a relatively low sensitivity for both coagulase-positive staphylococci and S. agalactiae , making these poor screening tests for the presence of these pathogens within a dairy herd.

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.

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.

A cross-sectional study involving 1032 dairy farms in Ohio was conducted with the objective to evaluate the effectiveness of mastitis control measures in a contemporary dairy environment. Recently published observational studies have found varying effectiveness of common mastitis control practices, particularly nonlactating cow therapy (dry cow therapy, DCT).

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.

The objective of this report is to present preliminary results from a survey of producers regarding their use of mastitis control practices. However, the overall objective of a larger study, which will utilize the survey data summarized here, is to determine tbe economics of OCT. OCT economics will be considered conditional on the predominant mastitis agents in a herd. The study has three components: a microbiologic assessment of herd bulk tank samples, evaluation of herd SCC, and evaluation of herd mastitis control practices.