Source: CORNELL UNIVERSITY submitted to
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
Funding Source
Reporting Frequency
Accession No.
Grant No.
Project No.
Proposal No.
Multistate No.
Program Code
Project Start Date
Oct 1, 2008
Project End Date
Oct 1, 2010
Grant Year
Project Director
Bennett, G.
Recipient Organization
Performing Department
Non Technical Summary
Recently, there has been ample data provided on the presence of psychrotolerant Bacillus species and related spore formers in milk but little has been done to determine how they get in the milk in the first place. There is a need to determine whether on farm dairy management practices can influence the presence of psychrotolerant Bacillus species and related spore formers in bulk milk. This requires that researchers and extension specialists' work with dairy producers to determine which dairy management techniques are currently being used to improve milk quality. Psychrotolerant bacteria are present on many dairy operations and in many places. Management practices that can reduce or eliminate the psychrotolerant Bacillus from the bulk milk on the farm need to be identified. The expected outcomes are that the origin(s) of psychrotolerant Bacillus species and related spore formers will be determined on New York dairy operations. Another related goal is to determine which daily dairy management practices impact the concentration of psychrotolerant Bacillus species and related spore formers found in milk. Determining the origin will allow dairy producers to institute daily management practices that limit the presence of psychrotolerant Bacillus species and related spore formers in milk. By changing daily routines to limit the number of psychro-tolerant Bacillus and related spore formers in the milk, producers could achieve higher prices for their product through quality premiums from the processors. Dairy processors would also benefit from a more stable product, and product loss would be reduced. Consumers would gain the most by having high quality milk available for longer periods of time before it needed to be disposed of.
Animal Health Component
Research Effort Categories

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
Goals / Objectives
The dairy industry is a 1.6 billion dollar industry in New York as measured by sales of raw milk. The processing industry adds a considerable amount of value to this raw product. New York has seen a growth in manufacturing plants in the last 10 years; many of these operate in the fluid milk industry. Spoilage of pasteurized milk is not only a direct loss to the industry, but has an indirect negative effect on the consumer's perception about dairy products. Shelf life of pasteurized milk is impacted by the quality of the raw milk. Spoilage of milk by microbial elements such as psychrotolerant Bacillus species and related spore formers are considered a major factor in the shelf life of milk. Previous research suggests that very low numbers of psychrotropic sporeforming bacteria are likely to be present in bulk tank milk, hence determining the sources of these microbes represents a considerable challenge (Boor et al., 1998). Psychrotrophic bacteria have an optimum growth temperature that is colder than most bacteria, so these bacteria are able to multiply and cause spoilage of milk in the refrigerator. Psychrotrophic bacteria may release lipolytic and proteolytic enzymes that break down fat and protein and give milk off flavors. Control of psychrotolerant Bacillus species and related spore formers in milk may lead to increased shelf life of pasteurized milk. Milk spoilage is a large part of consumer complaints in the retail industry. Consumers will clearly benefit from this improved shelf life through better tasting and more appetizing milk products. We intend to identify the origin of psychrotolerant Bacillus species and related spore formers on New York state dairy operations. We intend to identify dairy farm management practices that either increase or decrease the presence of these bacteria in bulk milk. This will be done in conjunction with the help of microbiologists, epidemiologists, extension specialists, and animal scientists working in unison with New York dairy producers to improve the overall quality of pre-pasteurized milk. The objective of this study is to twofold: 1. Determine the overall presence of psychrotolerant Bacillus species and related spore formers in bulk milk from New York dairy farms; and 2. Determination of management factors on New York dairy farms that are associated with production of low counts of Bacillus species in the bulk milk.
Project Methods
Approximately 100 dairy farms will be selected for this study throughout New York State. Farms will be selected from the visit roster of the four QMPS laboratories in the four main dairy regions of New York State (Central, West, North and East). Farms will be selected to represent the full spectrum of milk quality (low and high bulk milk somatic cell count) and the spectrum of herd sizes seen in New York State. Dairy producers will be asked a list of predetermined questions about their current dairy management practices with the intent of finding dairy management practices that may either increase or decrease the presence of psychrotolerant Bacillus species and related spore formers in milk. Identification of the potential sources of the psychrotolerant Bacillus species on the dairy farm is of key importance. Bulk milk samples (three 40 ml vials) will be taken aseptically at each dairy operation on the same day that a detailed management questionnaire will be completed. Psychrotolerant Bacillus species and related spore formers will be quantified through microbiological analyses of bulk tank milk samples. Specifically, samples will be evaluated for standard plate count (SPC) and psychrotrophic bacteria count (PBC) according to procedures outlined in the Standard Methods for the Examination of Dairy Products. After sample aliquots are removed for initial microbiological analyses, the remaining samples will be thoroughly mixed and 200 ml aliquots will be transferred into sterile 250 ml screw-cap Pyrex bottles, then heat-treated at 80 degrees C for 12 minutes to reduce background flora (i.e., vegetative cells) and cooled immediately on ice. All heat-treated samples will be stored at 6 degrees C and plated on days 1, 7 and 14 post-collection. For each sample, bacterial colonies will be visually examined and colonies with distinct morphologies will be selected and streaked for purity on Brain Heart Infusion agar. Purified isolates will be characterized for Gram reaction using a 3-step Gram stain kit and frozen at -80 degrees C in 15% glycerol. Bacteria will be identified by DNA sequencing of either or both rpoB and 16S rDNA. The questionnaire will serve the purpose of gaining background information on the management practices carried out by dairy producers and the potential impact these practices have on the presence of psychrotolerant Bacillus species and related spore formers in milk. The questionnaire being used is based on the one currently used by Quality Milk Production Services and will be administered by a trained staff member from Quality Milk Production Services. Additional questions that relate to potential risk factors for the presence of psychrotolerant Bacillus species and related spore formers have been added to the survey. All surveys will be filled out during an interview done in person on the same day as milk sample collection takes place. Statistical analysis will be done to relate the bulk milk findings to the survey results. Regression analysis will be performed to evaluate the most significant factors associated with bulk milk psychrotolerant bacteria counts.

Progress 10/01/08 to 10/01/10

OUTPUTS: We completed surveys on 100 dairy farms in New York. All farms were visited, a questionnaire was completed and bulk milk samples were taken and analyzed for sporeforming organisms. We observed a large variability in the number of sporeforming bacteria between farms. With the survey on management factors that we performed at the time of sampling, we were able to connect management practices to sporeformer quantity. The main factors associated with sporeformers were cow hygiene, milk filter hygiene, bulk milk somatic cell count and stall hygiene. Results were reported back to the dairy farms. In the second year, we selected the 10 farms with the highest count of sporeforming organisms and the 10 farms with the lowest count of sporeforming organisms. These 20 farms were followed on a monthly basis for a full year. Every month milk samples and management practices were recorded. The seasonality of the count of sporeforming organisms was studies PARTICIPANTS: At Cornell University the following participated: Dr Ynte Schukken Dr Gary Bennett Dr Kathryn Boor Dr Martin Wiedmann Ms Stephanie Massielo Mr Brad Rauch. Several field technicians at Quality Milk Production Services contributed to this project by collecting data on the farms. TARGET AUDIENCES: Dairy Farmers Dairy Veterinarians Dairy processors PROJECT MODIFICATIONS: No major modifications have taken place. The project went according to plan and was very successful. We have obtained additional funding to continue the project with a second set of dairy farms and work on intervention programs to reduce sporeformers in bulk tank milk.

A very important difference was observed between farms. Some farms have very high quality milk with very few sporeforming bacteria. Other farms have much higher counts. The sporeformer count is related to but certainly not strongly correlated with other milk quality parameters such as somatic cell count and bacteria counts. This points towards additional factors directly associated with sporeformer count. The dairy processing industry has shown a great interest in these results as sporeformers have a major impact on shelf life of dairy products. Presentations on the results have been presented to dairy farmers, dairy veterinarians and the dairy processing industry. In total approximately 700 individuals have been reached. The most important finding in the second and final year of the study was that farms that have high counts of sporeformers tend to have high counts throughout the year. similarly, farms with low counts tend to have these low counts consistently throughout the year. The implication of this is that we will be able to identify farms with these milk characteristics on a consistent bases. It will also allow us to work with these farms to improve milk quality.


  • Identification and Characterization of Psychrotolerant Sporeformers Associated with Fluid Milk Production and Processing. Ivy RA, Ranieri ML, Martin NH, den Bakker HC, Xavier BM, Wiedmann M, Boor KJ. Appl Environ Microbiol. 2012 Jan 13. [Epub ahead of print]
  • Results from raw milk microbiological tests do not predict the shelf-life performance of commercially pasteurized fluid milk. Martin NH, Ranieri ML, Murphy SC, Ralyea RD, Wiedmann M, Boor KJ. J Dairy Sci. 2011 Mar;94(3):1211-22.

Progress 10/01/08 to 09/30/09

OUTPUTS: The first year of the project was focused on data collection in the field. In the first year we have enrolled 88 out of the 100 herds. PARTICIPANTS: Partners on the project were: Quality Milk Productions Services at Cornell University. Department of Animal Science and Food Science at Cornell University. so far 88 dairy farmers have been enrolled in the project. TARGET AUDIENCES: The target audience for this project are dairy farmers. The first year of the project was focused on data collection. Two presentations on the project were presented to dairy farmers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Two presentation were given to NY dairy producers about the project. A total of 55 dairy farmers were present at the meetings.


  • No publications reported this period