By Ginger D Fenton
Setting up a laboratory to assess raw milk quality and finished dairy products on the farm is an undertaking that can require additional equipment and technical knowledge.
On-farm culturing is a tool used by many dairy producers to gain insight into the potential causes of mastitis on their farms. Culturing on the farm can allow for more rapid treatment as preliminary test results are available within 24 to 48 hours. The added information on the potential cause of mastitis also can provide direction for treatment decisions depending on the protocols that the farm has developed in cooperation with their herd veterinarian. The cost of needed equipment is relatively inexpensive, and the required training is accessible through Extension workshops and online trainings.
Given the ease of use and utility of on-farm culturing, can producers use it for their bulk tank milk? This is a common question when there is a discussion about on-farm culturing. The short answer is “no”. On-farm culturing for mastitis pathogens provides information based on a small sample of milk obtained from a single quarter or possibly a pooled sample from multiple quarters from the cow. The results indicate the presence of pathogens that may be the cause of mastitis. Different culturing systems provide different information, so the results depend on the system that is used. If a bulk tank sample is cultured using a quad plate, tri plate, or another system, any pathogen from any cow’s milk in the bulk tank could be grown on the plate. The results would be extremely difficult, if not impossible, to interpret due to overgrowth and the potential for many pathogens and non-pathogenic bacteria introduced during milking to be present.
Another question on the same train of thought is: should an on-farm processor set up a laboratory to test their milk and products? In a laboratory setting, a bulk tank milk sample is methodically diluted and plated multiple times to quantify the bacteria present. The sample is plated on various media to quantify specific groups of bacteria that are present such as coliform bacteria or aerobic bacteria with the standard plate count (SPC). Other commonly reported measures of milk quality include laboratory pasteurization count (LPC), and preliminary incubation count (PI). Some reports will list counts for Staphylococcus species and Streptococcus species possibly with additional analysis for environmental Staph spp. and Strep spp. counts. Upon request, some laboratories can test for specific pathogens such as Listeria monocytogenes, Salmonella species, and Mycoplasma species.
To ensure that these tests will detect and quantify the intended species or groups of bacteria, established protocols are detailed in manuals that are listed in the Resources section. Protocols exist for collecting samples throughout the continuum of handling milk from the cow to the finished dairy products. A laboratory should have the necessary supplies in their stock and understand the techniques for proper sample collection and storage to minimize the chance of contamination.
Processing the sample adds another layer of procedures, expenses, and time. Depending on the test being run, incubation times and temperatures could vary which may require more than one incubator. The person performing the test needs to draw on technical knowledge and pay attention to detail. The results of much of the testing performed at the farm level are presumptive or suspect. Confirmation of the presence of certain pathogens in a sample is conducted by sending a sample to a certified laboratory. It is very cost-prohibitive, time-consuming, and can be tedious to perform the confirmatory tests. A certified laboratory is prepared to conduct confirmatory testing for pathogens.
Aside from incubators, other equipment and supplies may be needed including a water bath or heat block to hold a sample at a high temperature such as for determining the LPC, a vortex for mixing samples as dilutions are performed, as well as basic supplies including loops, tubes, and spreaders. A hood will aid in safety and reduce possible contamination. Making the media for the tests requires additional equipment and supplies such as beakers, hot plates, and possibly an autoclave. The alternative is to purchase media that is already prepared and store until use. Keep in mind that media and reagents have a timeframe for use.
An autoclave may be needed to sterilize equipment and media and for safe disposal of biohazard waste. Some disposable supplies such as loops and tubes can be used but waste disposal is still a major consideration. The safety of the personnel is imperative. Proper training in handling pathogens and operating lab equipment safely is required. Also, consider how access to the lab will be controlled. Local and state regulations should be considered as well. It is possible to contract this service to an outside provider.
There are alternate solutions for working around the need for certain equipment and supplies in setting up a laboratory. Careful weighing of the reasons for the laboratory, the expertise needed to operate the lab, and the analyses that will be performed in the lab can guide the decision as to whether a laboratory is right for a value-added enterprise or whether it makes more sense to contract testing services with an outside laboratory. Setting up a laboratory to assess raw milk quality and finished dairy products on the farm is an undertaking that can require additional equipment and technical knowledge. Many factors should be considered to make the determination if the desired savings in time and money along with the utility of the laboratory will outweigh the costs.
Source : psu.edu