Lawrence E. Heider

Environmental and managerial determinants of somatic cell counts and clinical mastitis incidence in Ohio dairy herds

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).

Clinical mastitis and intramammary infections on Ohio dairy farms

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%.

Bacterial and Somatic Cell Counts in Bulk Tank Milk from Nine Well Managed Herds1

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.

Use of Bulk Tank and Milk Filter Cultures in Screening for Streptococcus agalactiae and Coagulase-positive Staphylococci

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.

Environmental and managerial risk factors of intramammary infection with coagulase-negative staphylococci in Ohio dairy herds

Abstract A stratified random sample of Ohio dairy herds was studied to relate herd management and environmental conditions to the prevalence of intramammary infection with coagulase-negative staphylococci. Management and environmental conditions were assessed by investigator observation and by interview with the dairy producers. Separate analyses for each of 70 management and environmental independent variables identified many potential disease determinants. Analysis of covariance models were developed to predict the prevalence of coagulase-negative staphylococci. The first model used seven model degrees of freedom, had an R -squared of 0.62, and included the following independent variables: use of a cloth for washing cows, use of a hypochloride- or iodine-based post-milking teat dip, a population of milking cows less than 50, the amount of bedding provided, use of free stall housing, an interaction between a small herd size and the amount of bedding provided and an interaction between the use of free stalls and the type of post-milking teat dip. The second model had an R -squared of 0.54 and was reduced to five model degrees of freedom by exclusion of the variables for use of free stalls and the interaction between free stalls and type of post-milking teat dip.

Determinants of high somatic cell count prevalence in dairy herds practicing teat dipping and dry cow therapy and with no evidence of Streptococcus agalactiae on repeated bulk tank milk examination

Abstract A series of least squares analytical models were developed in a cross-sectional epidemiologic study of observed variability in within-herd high milk somatic cell count (SCC) prevalence. The study population was restricted to Ohio (U.S.A.) dairy cow herds where post-milking antiseptic teat dipping and prophylactic dry cow antibiotic therapy of all cows were practiced. Additionally, no Streptococcus agalactiae was isolated from repeated bulk tank milk screening of these herds. The first analysis considered 12-month herd average high SCC prevalence as the dependent variable. The second analysis narrowed the herd average calculation to a 3-month or seasonal interval, while the third analysis included age adjustment of the 3-month rolling herd average high SCC prevalence. All of the models identified significant main effects and significant first order interactions of main effects. Milking order was a significant factor in all models, as were four interactions: washing teats only and rinsing teat cups between cows; washing with a common cloth or sponge and milking order; washing teats only and elapsed time between udder preparation and teat cup attachment; and elapsed time between udder preparation and teat cup attachment, and rinsing teat cups between cows.

The use of high somatic cell count prevalence in epidemiologic investigations of mastitis control practices

A series of least-squares analytical models were developed in a cross-sectional epidemiologic study of the observed variability in within-herd high somatic cell count (SCC) prevalence, a measure of mastitis prevalence in dairy herds. The dependent variable, high SCC prevalence, was calculated as the 12-month rolling herd average percentage of lactating cows with milk SCC in excess of 283 000 cells ml−1. The first analysis involved the results of a bacteriologic survey of bulk-tank milk samples for the presence of Streptococcus agalactiae and coagulase-positive staphylococci, the two most common contagious intramammary pathogens. The presence of either pathogen in bulk-tank samples was associated with significantly higher high SCC prevalence. The second analysis involved responses to a questionnaire concerning management and mastitis control practices. Both the practices of post-milking teat dopping and dry-cow antibiotic therapy were associated with significantly lower high SCC prevalence. The third analysis combined the data collected for the first two analyses so that the independent variables included both bulk-tank bacteriologic results and management and mastitis control practices. This model was able to explain a greater proportion of the variability in high SCC prevalence than either of the other two models. There were three variables associated with significant decreases in high SCC prevalence namely the absence of Streptococcus agalactiae in the bulk tank milk, the adoption of post-milking teat dipping and the practice of dry-cow antibiotic therapy of all cows. Milk somatic cell counting is now widely accepted and practiced in many countries, and individual-cow SCC data are available from large numbers of herds at a minimal expense. By corroborating the role of post-milking teat dipping and dry-cow antibiotic therapy in mastitis control programs, this study establishes the usefulness of high SCC prevalence data for epidemiologic studies of mastitis control practices.

The Critical Need for Federal Legislation to Provide for the Expansion of the Veterinary Workforce

American veterinary medical education stands at a crucial point. To maintain the status quo and to meet ever-increasing societal needs within the United States and globally, it is essential that the veterinary medical profession expand its horizons and capabilities. If it does not, it will lose its current status. The profession faces a crucial shortage in the workforce it needs both to continue to perform its current functions and, more importantly, to meet its growing responsibilities. This is not a new situation, and the profession can learn from its past successes and failures. Action is necessary. The profession has the capability and expertise to meet these challenges, but it must activate these skills in order to succeed.

Association of American Veterinary Medical Colleges (AAVMC): 50 Years of History and Service

The mission of the Association of American Veterinary Medical Colleges (AAVMC) is to advance the quality of academic veterinary medicine. Founded in 1966 by the 18 US colleges of veterinary medicine and 3 Canadian colleges of veterinary medicine then in existence, the AAVMC is celebrating 50 years of public service. Initially, the AAVMC comprised the Council of Deans, the Council of Educators, and the Council of Chairs. In 1984, the tri-cameral structure was abandoned and a new governing structure with a board of directors was created. In 1997, the AAVMC was incorporated in Washington, DC and a common application service was created. Matters such as workforce issues and the cost of veterinary medical education have persisted for decades. The AAVMC is a champion of diversity in the veterinary profession and a strong advocate for One Health. The AAVMC has adopted a global perspective as more international colleges of veterinary medicine have earned COE accreditation and become members.